សំណួរត្រៀម_សម្រាប់ការប្រឡងថ្នាក់វេជ្ជបណ្ឌិតឯកទេស_2024 PDF
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This document contains practice questions for a medical doctor specialization exam in 2024, focusing on basic science topics, such as virology, HIV and related diseases. The questions cover topics including virus types, infections, symptoms, and treatment. Preparing for the exam by solving these practice questions may improve the test-taker's understanding and ultimately improve the chance of success.
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ផ្នែកទី ១ Basice Science No Question An HIV-positive patient asks you if you can tell him the chances of him progressing to 1 symptomatic AIDS. Which one of the following tests would be most useful? A CD4 lymph...
ផ្នែកទី ១ Basice Science No Question An HIV-positive patient asks you if you can tell him the chances of him progressing to 1 symptomatic AIDS. Which one of the following tests would be most useful? A CD4 lymphocyte count B HIV antibody test C HIV RT PCR D HIV p24 antigen ANSWER: C Which of the following viruses causes an acute febrile rash and produces disease in 2 immunocompetent children but has been associated with transient aplastic crises in persons with sickle cell disease? A Rubeola B Varicella-zoster C Parvovirus D Rubella ANSWER: C Infection with herpes simplex virus, a common human pathogen, is best described by 3 which of the following statements? A The CNS and visceral organs are usually involved B It rarely recurs in a host who has a high antibody titer C It can be reactivated by emotional disturbances or prolonged exposure to sunlight D Initial infection usually occurs by intestinal absorption of the virus ANSWER: C The latest and most effective therapy for AIDS patients includes azidothymidine (AZT), 4 dideoxyinosine (DDI), and saquinavir or similar agents. Use of these three drugs would inhibit which of the following viral processes? A RNase, DNase B gp120 formation C p24 antibody expression D Reverse transcriptase, protease ANSWER: D An HIV-positive patient prior to being treated with AZT, DDI, and saquinavir has a CD4 lymphocyte count and an HIV RNA viral load test done. Results are as follows: CD4: 50 5 CD4 lymphocytes per microliter HIV RNA: 750,000 copies per ml Which of the following statements best describes the above patient? A This patient is no longer in danger of opportunistic infection B The 5-year prognosis is excellent C The patient’s HIV screening test is most likely negative The viral load of 750,000 copies per ml suggests that the patient will respond to triple D therapy ANSWER: D This HIV-positive patient with a viral load of 750,000 copies of HIV RNA/ml and a total CD4 count of 50 is at an increased risk for a number of infectious diseases. For which of 6 the following diseases is the patient at no more added risk than an immunocompetent host? A Pneumocystic pneumonia B Mycobacterial disease C Kaposi’s sarcoma D Pneumococcal pneumonia ANSWER: D Infectious mononucleosis, a viral disorder that can be debilitating, is characterized by 7 which of the following statements? A It is most prevalent in children less than 14 years old B It is caused by a rhabdovirus C The causative pathogen is an Epstein-Barr virus D Affected persons respond to treatment with the production of heterophil antibodies ANSWER: C A tube of monkey kidney cells is inoculated with nasopharyngeal secretions. During the next 7 days, no cytopathic effects (CPEs) are observed. On the eighth day, the tissue 8 culture is infected accidentally with a picornavirus; nevertheless, the culture does not develop CPEs. The most likely explanation of this phenomenon is that A The nasopharyngeal secretions contained hemagglutinins B The nasopharyngeal secretions contained rubella virus C Picornavirus does not produce CPEs D Picornavirus does not replicate in monkey kidney cells ANSWER: B The clinical picture of arbovirus infection fits one of three categories: encephalitis, 9 hemorrhagic fever, or fever with myalgia. One of the characteristics of arboviruses is that they A Are transmitted by arthropod vectors B Are usually resistant to ether C Usually cause symptomatic infection in humans D Are closely related to parvoviruses ANSWER: A Which one of the following statements best describes interferon’s suspected mode of 10 action in producing resistance to viral infection? A It stimulates a cell-mediated immunity B It stimulates humoral immunity C Its direct antiviral action is related to the suppression of messenger RNA formation D Its action is related to the synthesis of a protein that inhibits translation or transcription ANSWER: D Coronaviruses are recognized by club-shaped surface projections that are 20 nm long and 11 resemble solar coronas. These viruses are characterized by their ability to A Infect infants more frequently than adults B Cause the common cold C Grow well in the usual cultured cell lines D Grow profusely at 50°C ANSWER: B Which of the following antiviral agents is a purine nucleoside analogue that has shown 12 promise with Lassa fever, influenza A and B, and respiratory syncytial virus (RSV)? A Amantadine B Rimantadine C Vidarabine D Ribavirin ANSWER: D 13 Echoviruses are cytopathogenic human viruses that mainly infect the A Respiratory system B Central nervous system C Blood and lymphatic systems D Intestinal tract ANSWER: D The most sensitive test for the diagnosis of herpes simplex (HSV) 14 meningitis in a newborn infant is A HSV IgG antibody B HSV polymerase chain reaction (PCR) C HSV culture D Tzanck smear ANSWER: B Acute hemorrhagic conjunctivitis (AHC) is a contagious ocular infection characterized by 15 pain, swelling of the eyelids, and subconjunctival hemorrhages. AHC has been reported to be caused by which of the following viruses? A Coronavirus B Reovirus C Rhinovirus D Enterovirus ANSWER: D Mumps virus accounts for 10 to 15% of all cases of aseptic meningitis in the United 16 States. Infection with mumps virus A Is preventable by immunization B Will usually cause mumps orchitis in postpubertal males C Is maintained in a large canine reservoir D Usually produces severe systemic manifestations ANSWER: A The serum of a newborn infant reveals a 1:32 cytomegalovirus (CMV) titer. The child is 17 clinically asymptomatic. Which of the following courses of action would be advisable? A Repeat the CMV titer immediately B Obtain an anti-CMV IgM titer from the baby C Obtain a CMV titer from all siblings D Obtain an anti-CMV IgM titer from the mother ANSWER: B A 3-year-old child presents at the physician’s office with symptoms of coryza, 18 conjunctivitis, low-grade fever, and Koplik’s spots. The causative agent of this disease belongs to which group of viruses? A Adenovirus B Herpesvirus C Picornavirus D Paramyxovirus ANSWER: D One of the most common sexually transmitted diseases that may lead to cervical 19 carcinoma is caused by which of the following viruses? A Cytomegalovirus B Papillomavirus C Epstein-Barr virus D Herpes simplex virus ANSWER: B Which virus is the leading cause of the croup syndrome in young children and, when 20 infecting mammalian cells in culture, will hemabsorb red blood cells? A Group B coxsackievirus B Rotavirus C Parainfluenza virus D Adenovirus ANSWER: C Hepatitis E, a recently characterized hepatitis virus, is best described by which of the 21 following statements? A It is not a threat to the blood supply B It is a major cause of blood-borne hepatitis C It is prevalent in North America D It is a single-stranded DNA virus ANSWER: A Meningitis is characterized by the acute onset of fever and stiff neck. Aseptic meningitis 22 may be caused by a variety of microbial agents. During the initial 24 h of the course of aseptic meningitis, an affected person’s cerebrospinal fluid is characterized by A Decreased protein content B Elevated glucose concentration C Lymphocytosis D Polymorphonuclear leukocytosis ANSWER: D A nurse develops clinical symptoms consistent with hepatitis. She recalls sticking herself with a needle approximately 4 months before after drawing blood from a patient. 23 Serologic tests for HBsAg, antibodies to HBsAg, and hepatitis A virus (HAV) are all negative; however, she is positive for IgM core antibody. The nurse A Does not have hepatitis B B Has hepatitis A C Is in the late stages of hepatitis B infection D Is in the “window” (after the disappearance of HBsAg and before the appearance ANSWER: D Eastern equine encephalitis virus is associated with a high fatality rate. Control of the 24 disease could be possible by eradication of A Horses B Birds C Mosquitoes D Fleas ANSWER: C Adults who have had varicella as children occasionally suffer a recurrent form of the 25 disease, shingles. The agent causing these diseases is a member of which of the following viral families? A Herpesvirus B Poxvirus C Adenovirus D Myxovirus ANSWER: A 26 Rhinovirus is primarily transmitted by A Droplet aerosolization B Sexual activity C Fecal-oral route D Fomites ANSWER: D German measles virus (rubella), a common cause of exanthems in children, is best 27 described by which of the following statements? A Measles (rubeola) and German measles (rubella) are caused by the same virus B Incubation time is approximately 3 to 4 weeks C Vesicular rashes are characteristic D Onset is abrupt with cough, coryza, and fever ANSWER: D 28 The presence of Negri inclusion bodies in host cells is characteristic of A Mumps B Infectious mononucleosis C Congenital rubella D Rabies ANSWER: D Kuru is a fatal disease of certain New Guinea natives and is characterized by tremors and 29 ataxia; Creutzfeldt-Jakob disease (CJD) is characterized by both ataxia and dementia. These diseases are thought to be caused by A Slow viruses B Cell wall–deficient bacteria C Environmental toxins D Prions ANSWER: D According to recommendations issued by the U.S. Public Health Service, which of the 30 following statements regarding vaccination against smallpox is true? A Pregnant women should be vaccinated in the first trimester B Persons who have eczema should be vaccinated soon after diagnosis C Persons who have immune deficiencies should be vaccinated every 5 years D Persons traveling abroad need not be vaccinated ANSWER: D Hepatitis D virus (delta agent) is a defective virus that can replicate only in cells already 31 infected with which of the following viruses? A Hepatitis A virus B Epstein-Barr virus C Hepatitis G virus D Hepatitis B virus ANSWER: D A patient presents with keratoconjunctivitis. The differential diagnosis should include 32 infection with which of the following viruses A Parvovirus B Adenovirus C Epstein-Barr virus D Respiratory syncytial virus ANSWER: B A hospital worker is found to have hepatitis B surface antigen. Subsequent tests reveal 33 the presence of e antigen as well. The worker most likely A Is infective and has active hepatitis B Is infective but does not have active hepatitis C Is not infective D Is evincing a biologic false-positive test for hepatitis ANSWER: A 34 Alphavirus causes which one of the following viral diseases? A Marburg virus disease B St. Louis encephalitis C Western equine encephalitis D Dengue ANSWER: C Several antiviral compounds have been developed during the last decade. One such 35 compound is ribavirin, a synthetic nucleoside structurally related to guanosine. Ribavirin therapy has been successfully used against A Respiratory syncytial virus B Herpes simplex virus C Hepatitis B D Group A coxsackievirus ANSWER: A An immunocompromised person with history of seizures had an MRI that revealed a 36 temporal lobe lesion. Brain biopsy results showed multinucleated giant cells with intranuclear inclusions. The most probable cause of the lesion is A Hepatitis C virus B Herpes simplex virus C Listeria monocytogenes D Coxsackievirus ANSWER: B Which of the following procedures or clinical signs is most specific for the diagnosis of 37 infectious mononucleosis caused by the Epstein-Barr virus? Laboratory diagnosis is based on the presence of “atypical lymphocytes” and EBV- A specific antibody B Growth in tissue culture cells C Heterophile antibodies in serum D Lymphadenopathy and splenomegaly on physical examination ANSWER: B An infant, seen in the ER, presents with a fever and persistent cough. Physical 38 examination and a chest x-ray suggest pneumonia. Which of the following is most likely the cause of this infection? A Rotavirus B Adenovirus C Coxsackievirus D Respiratory syncytial virus ANSWER: D 39 Which one of the following groups of people may be at increased risk for HIV infection? A Members of a household in which there is a person who is HIV-positive B Receptionists at a hospital C Factory workers whose coworkers are HIV-positive D Foreign service employees who are hospitalized in Zaire for bleeding ulcers ANSWER: D An obstetrician sees a pregnant patient who was exposed to rubella virus in the 40 eighteenth week of pregnancy. She does not remember getting a rubella vaccination. The best immediate course of action is to A Terminate the pregnancy B Order a rubella antibody titer to determine immune status C Reassure the patient because rubella is not a problem until after the thirtieth week D Administer rubella immune globulin ANSWER: B Mad Cow Disease has been highly publicized in Great Britain. This disease, which is 41 similar to scrapie, is caused by A A prion B A virus C Rickettsiae D An autoimmune reaction ANSWER: A A patient has all the gastrointestinal symptoms of infection with hepatitis A virus (HAV), 42 yet all the tests for HAV-IgG and HAV-IgM are nonreactive. A possible cause of this infection is A Hepatitis B surface antigen B Hepatitis C C Hepatitis D D Hepatitis E ANSWER: D A 70-year-old nursing home patient refused the influenza vaccine and subsequently 43 developed influenza. She died of acute pneumonia 1 week after contracting the “flu.” The most common cause of acute postinfluenzal pneumonia is A Legionella B Listeria C Staphylococcus aureus D Klebsiella ANSWER: C 44 Which of the following viruses is primarily transmitted by the fecaloral route? A St. Louis encephalitis virus B Colorado tick fever virus C Coxsackievirus D Yellow fever virus ANSWER: C Hantavirus is an emerging pathogen that is best described by which of the following 45 statements? A Influenza-like symptoms are followed rapidly by acute respiratory failure B Hemolysis is common in infected patients C It is acquired by inhalation of aerosols of the urine and feces of deer D Transmission from human to human is common ANSWER: A 46 Erythema infectiosum (fifth disease), a self-limited disease of children, is caused by A Measles B Parvovirus C Rubella D Human herpesvirus type 6 ANSWER: B 47 Which one of the following viruses may be human tumor virus? A Epstein-Barr virus (EBV) B HIV C Papillomavirus D Varicella-zoster virus (VZV) ANSWER: C 48 Parvovirus infection, the cause of a mild exanthem in children, is characterized by A Epidemic acute respiratory disease B Gastroenteritis C Whooping cough–like disease D Acute hemolytic anemia ANSWER: D Cytomegalovirus (CMV) infection is common. Which one of the following statements 49 best characterizes CMV? A It can be transmitted across the placental barrier B While a common infection, CMV is almost always symptomatic C The CMV can be cultured from red blood cells of infected patients D Unlike other viral infections, CMV is not activated by immunosuppressive therapy ANSWER: A 50 Human rotaviruses are characterized by which of the following statements? A They produce an infection that is primarily seen in adults B They produce cytopathic effects in many conventional tissue culture systems C They are lipid-containing RNA viruses possessing a double-shelled capsid They can be sensitively and rapidly detected in stools by the enzyme-linked D immunosorbent assay (ELISA) technique ANSWER: D Subacute sclerosing panencephalitis virus (SSPE) is best described by which of the 51 following statements? A It is a progressive disease involving both white and gray matter B It is a late CNS manifestation of mumps C It is a common event occurring in 1 of 300,000 cases of mumps D Viral DNA can be demonstrated in brain cells ANSWER: A Rotavirus is a double-stranded RNA virus with a double-walled capsid. Which one of the 52 following statements best describes rotavirus? A There are no related animal viruses B It is a major cause of neonatal diarrhea C It is readily cultured from the stool of infected persons D Maternal antibody does not appear to be protective ANSWER: B 53 Paramyxoviruses are most commonly associated with which of the following diseases? A Fifth disease B Rubella C Croup D Tonsillitis ANSWER: C 54 Human papillomavirus is most commonly associated with A Rectal polyps B Prostate cancer C Condyloma acuminatum D Hepatic carcinoma ANSWER: D Reverse transcriptase is an enzyme unique to the retroviruses. Which one of the following 55 is a function of the enzyme reverse transcriptase? A DNase activity B RNA-dependent RNA polymerase activity C RNA isomerase activity D RNA-dependent DNA polymerase activity ANSWER: D St. Louis encephalitis, a viral infection, was first recognized as an entity in 1933. Which 56 of the following best describes SLE? A It is transmitted to humans by the bite of an infected tick B It is caused by a togavirus C It is the major arboviral cause of central nervous system infection in the United States D It may present initially with symptoms similar to influenza ANSWER: C There is considerable overlap of signs and symptoms seen in congenital and perinatal infections. In a neonate with “classic” symptoms of congenital cytomegalovirus (CMV) 57 infection, which one of the following tests would be most useful in establishing a diagnosis? A CMV IgG titer on neonate’s serum at birth B CMV IgG titer on mother’s serum at birth of infant C CMV IgM titer on neonate’s serum at birth and at 1 month of age D Total IgM on neonate’s serum at birth ANSWER: C Interferon, a protein that inhibits viral replication, is produced by cells in tissue culture 58 when the cells are stimulated with which of the following? A Botulinum toxin B Synthetic polypeptides C Viruses D Chlamydiae ANSWER: C Which one of the following statements best describes the cytopathic effects of viruses on 59 host cells? A Usually morphological in nature B Often associated with changes in mitochondrial membranes C Pathognomonic for an infecting virus D Rarely fatal to the host cell ANSWER: A A 17-year-old girl presents with cervical lymphadenopathy, fever, and pharyngitis. 60 Infectious mononucleosis is suspected. The most rapid and clinically useful test to make this diagnosis is A IgM antibody to viral core antigen (VCA) B IgG antibody to VCA C Antibody to Epstein-Barr nuclear antigen (EBNA) D Culture ANSWER: A 61 Which one of the following viruses would be most likely to establish a latent infection? A Adenovirus B Measles virus C Influenza virus D Parvovirus ANSWER: A A regimen that includes appropriately administered gamma globulin may be 62 contraindicated in which one of the following diseases? A Hepatitis A B Hepatitis B C Rabies D Infectious mononucleosis ANSWER: D 63 Atypical lymphocytosis is most likely to be found in which one of the following diseases? A Encephalitis caused by herpes simplex virus (HSV) B Mononucleosis induced by Epstein-Barr virus C Parvovirus infection D Chronic hepatitis C ANSWER: B A patient has arthralgia, a rash, lymphadenopathy, pneumonia but no fever. Which of the 64 following diseases is most likely based on these symptoms? A Dengue fever B St. Louis encephalitis C Infectious mononucleosis D Hepatitis ANSWER: A Hepatitis C (HCV) is usually a clinically mild disease, with only minimal elevation of 65 liver enzymes. Hospitalization is unusual. Which one of the following statements best characterizes HCV? A Few cases progress to chronic liver disease B It often occurs in posttransfusion patients C HBV but not HCV infections occur in IV drug abusers D It is a DNA virus ANSWER: B Which of the following markers is usually the first viral marker detected after hepatitis B 66 infection? A HBeAg B HBsAg C HBcAg D Anti-HBc ANSWER: B Which of the following may be the only detectable serological marker during the early 67 convalescent phase of HBV infection (window phase)? A HBeAg B HBsAg C HBcAg D Anti-HBc ANSWER: D Which one of the following markers is closely associated with HBV infectivity and DNA 68 polymerase activity? A HBeAg B HBsAg C HBcAg D Anti-HBc ANSWER: A Which of the following is found within the nuclei of infected hepatocytes and not usually 69 in the peripheral circulation? A HBeAg B HBsAg C HBcAg D HbeAb ANSWER: D 70 Which one of the following viruses is the leading cause of congenital malformations? A Rabies B Rhinovirus C Cytomegalovirus D Respiratory syncytial virus ANSWER: C 71 Orchitis, which may cause sterility, is a possible manifestation of which of the following? A Rabies B Rhinovirus C Cytomegalovirus D Mumps ANSWER: D 72 Which of the following is a leading cause of pneumonia primarily in infants? A Rabies B Rhinovirus C Cytomegalovirus D Respiratory syncytial virus ANSWER: D 73 Which of the following causes a fatal encephalitis for which a vaccine is available? A Rabies B Rhinovirus C Cytomegalovirus D Respiratory syncytial virus ANSWER: A Traditional vaccination for the common cold is virtually impossible because there are 74 multiple serotypes of which one of the following viruses? A Rabies B Rhinovirus C Cytomegalovirus D Respiratory syncytial virus ANSWER: B 75 Which of the following is available and effective for hepatitis A? A Acyclovir B Killed virus vaccine C Inactivated virus vaccine D Live virus vaccine ANSWER: B Patients should be vaccinated annually for influenza with which of the following 76 vaccines? A Immune serum globulin B Killed virus vaccine C Inactivated virus vaccine D Live virus vaccine ANSWER: C 77 The vaccine for measles is best characterized as a A Bacterin B Killed virus vaccine C Inactivated virus vaccine D Live virus vaccine ANSWER: D 78 Which one of the following would be the treatment of choice for HSV infection? A Acyclovir B Killed virus vaccine C Herpes immune globulin D Azythromycin ANSWER: A 79 Which of the following best describes the presently available vaccine for hepatitis B? A Synthetic peptide vaccine B Killed virus vaccine C Inactivated virus vaccine D Recombinant viral vaccine ANSWER: D Chicken pox is a common disease of childhood. It is caused by which of the following 80 viruses? A Cytomegalovirus B Rotavirus C Varicella-zoster virus D Adenovirus ANSWER: C Excluding influenza, which one of the following viruses is a common cause of acute 81 respiratory disease? A Cytomegalovirus B Rotavirus C Varicella-zoster virus D Adenovirus ANSWER: D Human warts are not only cosmetically unsightly but may lead to cancer of the cervix. 82 They are caused by which one of the following viruses? A Cytomegalovirus B Rotavirus C Varicella-zoster virus D Papillomavirus ANSWER: D A vaccine is available for one of the most common causes of infantile gastroenteritis. 83 However, it has recently been recalled. The virus is A Cytomegalovirus B Rotavirus C Varicella-zoster virus D Adenovirus ANSWER: B A child has mononucleosis-like symptoms yet the test for mononucleosis and the EBV 84 titers are negative. One of the causes of heterophilenegative mononucleosis is A Cytomegalovirus B Herpes simplex virus C Varicella-zoster virus D Adenovirus ANSWER: A Malaise and fatigue with increased “atypical” lymphocytes and a reactive heterophil 85 antibody test is most commonly caused by A Toxoplasma B Borrelia burgdorferi C Epstein-Barr virus D Parvovirus ANSWER: C Lethargy, malaise, and fatigue are observed in a patient 2 weeks after eating raw 86 hamburger at a restaurant. The most likely infectious cause is A Toxoplasma B Cytomegalovirus C E. coli D Salmonella ANSWER: A Burkitt’s lymphoma is characterized by elevated “early antigen” tests with a restricted 87 pattern of fluorescence. This disease is caused by A Cytomegalovirus B B. burgdorferi C Epstein-Barr virus D Lymphogranuloma venereum ANSWER: C This virus may be detected by the polymerase chain reaction (PCR) in a variety of cells 88 of patients with nasopharyngeal carcinoma. A Measles B Mumps C Rubella D Parvovirus ANSWER: B This virus causes a mononucleosis-like syndrome caused by a latent herpesvirus; it is 89 often a congenital infection. Large amounts of the virus are excreted in the urine; thus, urine becomes the fluid of choice for diagnosis of this disease. A Epstein-Barr virus B Cytomegalovirus C HHV-6 D Parvovirus ANSWER: B Assume you are asked by a resident what the most appropriate specimen is for the 90 detection of a particular virus. Human papillomavirus A Cervical tissue B Synovial fluid C Blood D Skin ANSWER: A Assume you are asked by a resident what the most appropriate specimen is for the 91 detection of a particular virus. Cytomegalovirus A Cervical tissue B Synovial fluid C Blood D Skin ANSWER: C Assume you are asked by a resident what the most appropriate specimen is for the 92 detection of a particular virus. Enterovirus A Cervical tissue B Synovial fluid C Blood D Cerebrospinal fluid ANSWER: D Assume you are asked by a resident what the most appropriate specimen is for the 93 detection of a particular virus. Varicella-zoster virus (VZV) A Cervical tissue B Synovial fluid C Blood D Skin ANSWER: D Assume you are asked by a resident what the most appropriate specimen is for the 94 detection of a particular virus. Adenovirus 40/41 A Cervical tissue B Synovial fluid C Blood D Stool ANSWER: D Which of the following is transmitted by the fecal-oral route; can be acquired from 95 shellfish; and often causes acute jaundice, diarrhea, and liver function abnormalities? A Rotavirus B Adenovirus 40/41 C Norwalk virus D Hepatitis A virus ANSWER: D Which of the following is the second most common cause of pediatric gastroenteritis? 96 Unlike other similar viruses, this virus causes only gastroenteritis. A Rotavirus B Adenovirus 40/41 C Norwalk virus D Astrovirus ANSWER: B Which of the following is the most common cause of pediatric gastroenteritis? It is 97 difficult to grow in cell culture but can be detected easily by immunologic methods (ELISA). A Rotavirus B Adenovirus 40/41 C Norwalk virus D Astrovirus ANSWER: A Which of the following is a common cause of epidemic gastroenteritis, particularly 98 aboard cruise ships and in summer camps? It may be detected by ELISA methods or electron microscopy. A Rotavirus B Adenovirus 40/41 C Norwalk virus D Astrovirus ANSWER: C Which of the following is a cause of mild gastroenteritis? It can be transmitted by the 99 fecal-oral route but not by food consumption. A Rotavirus B Adenovirus 40/41 C Norwalk virus D Astrovirus ANSWER: D IgM antibody to the viral particle is the method of choice for laboratory diagnosis of 100 which one of the following hepatitis viruses? A Hepatitis A B Hepatitis B C Hepatitis C D Hepatitis D ANSWER: A This virus belongs to the family of flaviviruses and its reservoir is strictly human. 101 Transmission is blood-borne so the blood supply is routinely screened for this virus. A Hepatitis A B Hepatitis B C Hepatitis C D Hepatitis D ANSWER: C Vaccination for this hepatic disease is with viral surface antigen and usually provides 102 immunity. A Hepatitis A B Hepatitis B C Hepatitis C D Hepatitis D ANSWER: B This hepatitis virus is a calicivirus. The reservoir is in pigs, and humans acquire it via the 103 fecal-oral route. A Hepatitis A B Hepatitis B C Hepatitis C D Hepatitis E ANSWER: D This hepatitis virus is a defective virus in that it cannot replicate independently without 104 the presence of hepatitis B virus. A Hepatitis A B Hepatitis B C Hepatitis C D Hepatitis D ANSWER: D Which of the following is the causative agent of a variety of cutaneous warts (plantar, 105 common, and flat) and is associated with cervical neoplasia? A Human papillomavirus B West Nile virus C Tick-borne encephalitis virus D Polyomavirus ANSWER: A Recently appearing in the United States, this virus is carried by birds, transmitted by 106 mosquitoes, and infects humans and horses. A Human papillomavirus B West Nile virus C Tick-borne encephalitis virus D Polyomavirus ANSWER: B Which of the following viruses causes progressive multifocal leukoencephalopathy 107 (PML), a disease causing demyelination in the central nervous system? A Human papillomavirus B West Nile virus C Tick-borne encephalitis virus D Polyomavirus ANSWER: B 108 This virus is transmitted by the same arthropod that transmits babesiosis and ehrlichiosis. A Human papillomavirus B West Nile virus C Tick-borne encephalitis virus D Polyomavirus ANSWER: C This virus is a single-stranded RNA orthomyxovirus. Annual vaccination is necessary 109 because of antigenic drift and shift. A Measles virus B Influenza virus C Respiratory syncytial virus D Parainfluenza virus ANSWER: B This virus is a single-stranded RNA paramyxovirus. The rash known as Koplik’s spots is 110 pathognomonic. A Measles virus B Influenza virus C Respiratory syncytial virus D Parainfluenza virus ANSWER: A This virus is the leading cause of bronchiolitis and communityacquired pneumonia in 111 infants. A Measles virus B Influenza virus C Respiratory syncytial virus D Parainfluenza virus ANSWER: C 112 This is a paramyxovirus and causes the syndrome known as croup. A Measles virus B Influenza virus C Respiratory syncytial virus D Parainfluenza virus ANSWER: D This is a double-stranded DNA virus. It is responsible for 15% of pediatric respiratory 113 infections and 10 to 15% of acute diarrhea in children. A Measles virus B Influenza virus C Respiratory syncytial virus D Adenovirus ANSWER: D A patient with a peptic ulcer was admitted to the hospital and a gastric biopsy was performed. The tissue was cultured on chocolate agar incubated in a microaerophilic 114 environment at 37°C for 5 to 7 days. At 5 days of incubation, colonies appeared on the plate and were curved, Gramnegative rods, oxidase-positive. The most likely identity of this organism is A Campylobacter jejuni B Vibrio parahaemolyticus C Haemophilus influenzae D Helicobacter pylori ANSWER: D An inhibitor was designed to block a biologic function in H. influenzae. If the goal of the 115 experiment was to reduce the virulence of H. influenzae, the most likely target would be A Exotoxin liberator B Endotoxin assembly C Flagella synthesis D Capsule formation ANSWER: D An experimental compound is discovered that prevents the activation of adenyl cyclase 116 and the resulting increase in cyclic AMP. The toxic effects of which of the following bacteria might be prevented with the use of this experimental compound? A Vibrio cholerae B Corynebacterium diphtheriae C Pseudomonas D Listeria monocytogenes ANSWER: A There are millions of cases of leprosy (Hansen’s disease) worldwide, but predominately 117 in Asia and Africa. The clinical spectrum of Hansen’s disease is best characterized by A Immunologic anergy B Chronic pneumonitis C Peripheral neuritis D Bacilli in lesions that digest tissues ANSWER: C At a church supper in Nova Scotia, the following meal was served: baked beans, ham, coleslaw, eclairs, and coffee. Of the 30 people who attended, 4 senior citizens became ill in 3 days; 1 eventually died. Two weeks after attending the church supper, a 19-year-old 118 girl gave birth to a baby who rapidly became ill with meningitis and died in 5 days. Epidemiologic investigation revealed the following percentages of people who consumed the various food items: baked beans, 30%; ham, 80%; coleslaw, 60%; eclairs, 100%; and coffee, 90%. Which of the following statements is true? A This is not a case of food poisoning because only 4 people became ill A relationship between the death of the baby and the food consumed at the church supper B can be ruled out Based on the epidemiologic investigation, the eclairs can be isolated as the source of the C disease Additional epidemiologic data should include the percentage of those who ate a particular D food item who became ill ANSWER: D At a church supper in Nova Scotia, the following meal was served: baked beans, ham, coleslaw, eclairs, and coffee. Of the 30 people who attended, 4 senior citizens became ill in 3 days; 1 eventually died. Two weeks after attending the church supper, a 19-year-old girl gave birth to a baby who rapidly became ill with meningitis and died in 5 days. Epidemiologic investigation revealed the following percentages of people who consumed 119 the various food items: baked beans, 30%; ham, 80%; coleslaw, 60%; eclairs, 100%; and coffee, 90%. Which of the following statements is true? Microbiologic analysis revealed no growth in the baked beans, ham, or coffee; many Gram-positive beta-hemolytic, short, rod-shaped bacteria in the coleslaw; and rare Gram-positive cocci in the eclairs. The most likely cause of this outbreak is A Staphylococcus aureus B Listeria C Clostridium perfringens D Clostridium botulinum ANSWER: B A 21-year-old college student complained of malaise, low-grade fever, and a harsh cough, but not of muscle aches and pains. An x-ray revealed a diffuse interstitial pneumonia in 120 the left lobes of the lung. The WBC count was normal. The student has been ill for a week. Based on the information given, the most likely diagnosis is A Mycoplasma pneumonia B Pneumococcal pneumonia C Staphylococcal pneumonia D Influenza ANSWER: A A 21-year-old college student complained of malaise, low-grade fever, and a harsh cough, but not of muscle aches and pains. An x-ray revealed a diffuse interstitial pneumonia in 121 the left lobes of the lung. The WBC count was normal. The student has been ill for a week. Based on the information given, which of the following laboratory tests would most rapidly assist you in making the diagnosis? A Cold agglutinins B Viral culture C Complement fixation (CF) test D Gram stain of sputum ANSWER: A A 21-year-old college student complained of malaise, low-grade fever, and a harsh cough, but not of muscle aches and pains. An x-ray revealed a diffuse interstitial pneumonia in the left lobes of the lung. The WBC count was normal. The student has been ill for a week. The following laboratory data were available within 2 days: cold 122 agglutinins—negative; complement fixation (M. pneumoniae)—1:64; viral culture—pending, but negative to date; bacterial culture of sputum on blood agar and MacConkey’s agar—normal oral flora. In order to confirm the diagnosis, which of the following procedures could be ordered to achieve a specific and sensitive diagnosis? A Culture of the sputum on charcoal yeast extract B A repeat cold agglutinin test C A DNA probe to the 16S ribosomal RNA of an organism lacking a cell wall D A repeat CF test in 5 days ANSWER: C Pathogenic mechanisms involved in tuberculosis can be primarily attributed to which of 123 the following? A Toxin production by the mycobacteria B Specific cell adhesion sites C Cell-mediated hypersensitivity D Humoral immunity ANSWER: C The class of antibiotics known as the quinolones are bactericidal. Their mode of action 124 on growing bacteria is thought to be A Inhibition of DNA gyrase B Inactivation of penicillin-binding protein II C Inhibition of β-lactamase D Prevention of the cross-linking of glycine ANSWER: A Vancomycin-indeterminate S. aureus (VISA) has recently been reported in the United 125 States. Which one of the statements concerning VISA is the most correct? A Minimum inhibitory concentration (MIC) for vancomycin is at least 1.0 mcg/mL B VISA isolates are usually methicillin susceptible (methicillin-resistant S. aureus, MRSA) C VISAs have emerged because of the extended use of vancomycin for MRSAs D Patients with VISA isolates need not be isolated ANSWER: C A sputum sample was brought to the laboratory for analysis. Gram stain revealed the following: rare epithelial cells, 8 to 10 polymorphonuclear leukocytes per high-power 126 field, and pleomorphic Gram-negative rods. As the laboratory consultant, which of the following interpretations should you make? A The sputum specimen is too contaminated by saliva to be useful B There is no evidence of an inflammatory response C The patient has pneumococcal pneumonia D The patient has Vincent’s disease ANSWER: C An isolate from a wound culture is a Gram-negative rod identified as Bacteroides fragilis. 127 Anaerobic infection with B. fragilis is characterized by A A foul-smelling discharge B A black exudate in the wound C An exquisite susceptibility to penicillin D A heme-pigmented colony formation ANSWER: A Virtually all prokaryotic cells (bacteria, both Gram-positive and Gramnegative) contain 128 peptidoglycan as well as specific enzymes for its synthesis. All of the following statements concerning Gram-positive and Gram-negative bacteria are true except A The extent of cross-linking of peptidoglycan is a function of different species of bacteria B The peptidoglycan-synthesizing enzymes can be antibiotic targets Both Gram-positive and Gram-negative bacteria contain significant amounts of teichoic C acid With the exception of the structures that are cross-linked, peptidoglycan structure is D common to most bacteria ANSWER: C L. monocytogenes causes a variety of diseases, including food poisoning. Listeria are 129 small, Gram-positive, motile rod-shaped bacteria. Which of the following best describes these microorganisms? A Listeria are facultative intracellular pathogens B Once infected, the immune system cannot destroy Listeria C Listeria cannot be cultivated on artificial media D Flagella are produced both at room temperature and at 37°C ANSWER: A A 30-year-old male patient was seen by the emergency service and reported a 2-week 130 history of a penile ulcer. He noted that this ulcer did not hurt. Which one of the following conclusions/actions is most valid? A Draw blood for a herpes antibody test B Perform a dark-field examination of the lesion C Prescribe acyclovir for primary genital herpes D Even if treated, the lesion will remain for months ANSWER: B The laboratory reports that the Venereal Disease Research Laboratory (VDRL) test performed on the above patient is reactive at a dilution of 1:4 (4 dils). The patient also 131 reports to you that he has recently been diagnosed with hepatitis A. Which one of the following actions would be most appropriate? A Report this patient to the health department, as he has syphilis B Order a confirmatory test such as the fluorescent treponemal antibody test (FTA) C Repeat the VDRL test D Order a rapid reagin test (RPR) ANSWER: B In the above patient, which one of the following test combinations for syphilis is most 132 appropriate? A FTA-Abs (IgG)/FTA-Abs (IgM) B RPR/FTA-Abs C RPR/culture of the lesion D VDRL/RPR ANSWER: B Assume that the patient absolutely denied any contact, sexual or otherwise, with a person who had syphilis. Assume also that both the RPR and the FTA Abs were positive on this 133 patient. Which one of the following tests could be used to show that this patient probably does not have syphilis? A VDRL B Quantitative RPR C Treponema pallidum immobilization (TPI) test D Frei test ANSWER: C A 55-year-old man who is being treated for adenocarcinoma of the lung is admitted to a hospital because of a temperature of 38.9°C (102°F), chest pain, and a dry cough. Sputum 134 is collected. Gram’s stain of the sputum is unremarkable and culture reveals many small Gram-negative rods able to grow only on a charcoal yeast extract agar. This organism most likely is A Klebsiella pneumoniae B Mycoplasma pneumoniae C Legionella pneumophila D Chlamydia trachomatis ANSWER: C A patient was hospitalized after an automobile accident. The wounds became infected and the patient was treated with tobramycin, carbenicillin, and clindamycin. Five days 135 after antibiotic therapy was initiated, the patient developed severe diarrhea and pseudomembranous enterocolitis. Antibioticassociated diarrhea and the more serious pseudomembranous enterocolitis can be caused by A Clostridium sordellii B Clostridium perfringens C Clostridium difficile D S. aureus ANSWER: C Assuming that the average achievable serum level of gentamicin is 6 to 8 mcg/mL, which 136 of the following bacteria is susceptible to gentamicin? A E. coli with a minimal inhibitory concentration (MIC) of 10 mcg/mL B E. coli with an MIC of 12 mcg/mL C Klebsiella with an MIC of 0.25 mcg/mL D Klebsiella with an MIC of 6.0 mcg/mL ANSWER: C A child comes to an emergency room because of an infected dog bite. The wound is 137 found to contain small Gram-negative rods. The most likely cause of infection is A E. coli B H. influenzae C Pasteurella multocida D Brucella canis ANSWER: C A patient complained to his dentist about a draining lesion in his mouth. A Gram’s stain 138 of the pus showed a few Gram-positive cocci, leukocytes, and many branched Gram- positive rods. The most likely cause of the disease is A Actinomyces israelii B Actinomyces viscosus C Diphtheriae D Propionibacterium acnes ANSWER: A Group B streptococcus sepsis in an infant is preventable. Which one of the following 139 procedures is most likely to reduce the incidence of group B streptococcal disease? A Intrapartum antibiotic treatment B Use of a polysaccharide vaccine C Screening of pregnant females in the last trimester D Identification of possible high-risk births ANSWER: A There has been much speculation on the pathogenesis of group B streptococcal disease in 140 the neonate. One of the most likely pathogenic mechanisms is A Complement C5a, a potent chemoattractant, activates PMNs B The streptococci are resistant to penicillin C The alternative complement pathway is activated In the absence of specific antibody, opsonization, phagocyte recognition, and killing do D not proceed normally ANSWER: D A man who has a penile chancre appears in a hospital’s emergency service. The VDRL 141 test is negative. The most appropriate course of action for the physician in charge would be to A Send the patient home untreated B Repeat the VDRL test in 10 days C Perform dark-field microscopy for treponemes D Swab the chancre and culture on Thayer-Martin agar ANSWER: C Fever of unknown origin in a farmer who raises goats would most likely be caused by 142 which of the following organisms? A Brucella melitensis B Clostridium novyi C T. pallidum D Histoplasma capsulatum ANSWER: A Cholera is a toxicogenic dysenteric disease common in many parts of the world. In the 143 treatment of patients who have cholera, the use of a drug that inhibits adenyl cyclase would be expected to A Kill the patient immediately B Eradicate the organism C Increase fluid secretion D Block the action of cholera toxin ANSWER: D A box of ham sandwiches with mayonnaise prepared by a person with a boil on his neck 144 was left out of the refrigerator for the on-call interns. Three doctors became violently ill approximately 2 h after eating the sandwiches. The most likely cause is A S. aureus enterotoxin B Coagulase from S. aureus in the ham C S. aureus leukocidin D C. perfringens toxin ANSWER: A S. aureus causes a wide variety of infections, ranging from wound infection to 145 pneumonia. Treatment of S. aureus infection with penicillin is often complicated by the A Inability of penicillin to penetrate the membrane of S. aureus B Production of penicillinase by S. aureus C Production of penicillin acetylase by S. aureus D Lack of penicillin binding sites on S. aureus ANSWER: B Symptoms of C. botulinum food poisoning include double vision, inability to speak, and 146 respiratory paralysis. These symptoms are consistent with A Invasion of the gut epithelium by C. botulinum B Secretion of an enterotoxin C Endotoxin shock D Ingestion of a neurotoxin ANSWER: D In people who have sickle cell anemia, osteomyelitis usually is associated with which of 147 the following organisms? A Micrococcus B Escherichia C Pseudomonas D Salmonella ANSWER: D 148 The treatment of choice for a patient with C. jejuni enterocolitis is A Erythromycin B Ciprofloxacin C Ampicillin D Pepto-Bismol ANSWER: A A hyperemic edema of the larynx and epiglottis that rapidly leads to respiratory 149 obstruction in young children is most likely to be caused by A K. pneumoniae B M. pneumoniae C Neisseria meningitidis D H. influenzae ANSWER: D A 70-year-old female patient was readmitted to a local hospital with fever and chills following cardiac surgery at a major teaching institution. Blood cultures were taken and a 150 Gram-positive coccus grew from the blood cultures within 24 hours. Initial tests indicated that this isolate was resistant to penicillin. The most likely identification is A Streptococcus pneumoniae B Neisseria C Group A streptococcus D Enterococcus ANSWER: D A 70-year-old female patient was readmitted to a local hospital with fever and chills following cardiac surgery at a major teaching institution. Blood cultures were taken and a Gram-positive coccus grew from the blood cultures within 24 hours. Initial tests indicated 151 that this isolate was resistant to penicillin. Further testing revealed that the isolate possessed the group D antigen, was not β-lactamase-positive, but was resistant to vancomycin. The most likely identification of this isolate is A Enterococcus faecalis B Enterococcus durans C Enterococcus cassiflavus D Enterococcus faecium ANSWER: D Acute hematogenous osteomyelitis is often diagnosed by isolation of the organism from 152 the blood and is caused most often by A Proteus mirabilis B Streptococcus faecalis C Staphylococcus epidermidis D S. aureus ANSWER: D 153 Diphtheria toxin is produced only by those strains of C. diphtheriae that are A Glucose fermenters B Sucrose fermenters C Lysogenic for β-prophage D Of the mitis strain ANSWER: C A 28-year-old menstruating woman appeared in the emergency room with the following signs and symptoms: fever, 104°F (40°C); WBC, 16,000/μL; blood pressure, 90/65 154 mmHg; a scarlatiniform rash on her trunk, palms, and soles; extreme fatigue; vomiting; and diarrhea. The patient described in the case above most likely has A Scalded skin syndrome B Toxic shock syndrome C Guillain-Barré syndrome D Chickenpox ANSWER: B A 28-year-old menstruating woman appeared in the emergency room with the following signs and symptoms: fever, 104°F (40°C); WBC, 16,000/ μL; blood pressure, 90/65 155 mmHg; a scarlatiniform rash on her trunk, palms, and soles; extreme fatigue; vomiting; and diarrhea. Culture of the menstrual fluid in the case cited would most likely reveal a predominance of A S. aureus B S. epidermidis C C. perfringens D C. difficile ANSWER: A A 28-year-old menstruating woman appeared in the emergency room with the following signs and symptoms: fever, 104°F (40°C); WBC, 16,000/ μL; blood pressure, 90/65 156 mmHg; a scarlatiniform rash on her trunk, palms, and soles; extreme fatigue; vomiting; and diarrhea. The most characteristic finding not yet revealed in the case just presented would be A Travel to Vermont B Recent exposure to rubella C A retained tampon D Heavy menstrual flow ANSWER: C A new latex agglutination (LA) reagent for H. influenzae polysaccharide antigen in cerebrospinal fluid was evaluated. Results were compared with the isolation of H. 157 influenzae from the CSF. Results were as follows: LA POS, CULT POS: 25 LA POS, CULT NEG: 5 LA NEG, CULT POS: 5 LA NEG, CULT NEG: 95 The sensitivity of LA is A 0% B 30% C 85% D 95% ANSWER: C A new latex agglutination (LA) reagent for H. influenzae polysaccharide antigen in cerebrospinal fluid was evaluated. Results were compared with the isolation of H. 158 influenzae from the CSF. Results were as follows: LA POS, CULT POS: 25 LA POS, CULT NEG: 5 LA NEG, CULT POS: 5 LA NEG, CULT NEG: 95 The specificity of LA is A 0% B 30% C 80% D 95% ANSWER: D A new latex agglutination (LA) reagent for H. influenzae polysaccharide antigen in cerebrospinal fluid was evaluated. Results were compared with the isolation of H. 159 influenzae from the CSF. Results were as follows: LA POS, CULT POS: 25 LA POS, CULT NEG: 5 LA NEG, CULT POS: 5 LA NEG, CULT NEG: 95 The negative predictive value of LA is A 10% B 80% C 95% D 110% ANSWER: C A new latex agglutination (LA) reagent for H. influenzae polysaccharide antigen in cerebrospinal fluid was evaluated. Results were compared with the isolation of H. influenzae from the CSF. Results were as follows: LA POS, CULT POS: 25 LA POS, 160 CULT NEG: 5 LA NEG, CULT POS: 5 LA NEG, CULT NEG: 95 The incidence of H. influenzae meningitis in the general population is less than 1%. If during an epidemic the incidence rose to 3%, the negative predictive value of the LA test would A Increase B Decrease C Remain the same D Be impossible to calculate ANSWER: B Methicillin-resistant S. aureus (MRSA) was isolated from 7 patients in a 14-bed intensive 161 care unit. All patients were isolated and the unit closed to any more admissions. Which one of the following reasons best explains these rigorous methods to control MRSA? A MRSA is inherently more virulent than other staphylococci The alternative for treatment of MRSA is vancomycin, an expensive and potentially toxic B antibiotic C MRSA causes toxic shock syndrome MRSA spreads more rapidly from patient to patient than antibiotic-susceptible D staphylococci do ANSWER: B A patient with AIDS returned from Haiti with acute diarrhea. The stool revealed an oval 162 organism (8 to 9 μm in diameter) that was acid-fast and fluoresced blue under ultraviolet light. The most likely identification of this organism is A Cyclospora B Giardia C Enterocytozoon D Cryptosporidium ANSWER: A A 2-year-old infant is brought to the emergency room with hemolytic uremic syndrome 163 and thrombocytopenia. Which one of the following bacteria would most likely be isolated from a stool specimen? A Shigella B Salmonella C Aeromonas D E. coli 0157/H7 ANSWER: D E. coli causes disease by a variety of different methods. Which one of the following E. 164 coli types is characterized by the presence of LT (heat-labile) and ST (heat-stable) proteins? A Enteroinvasive (EIEC) B Enterotoxigenic (ETEC) C Enterohemorrhagic (EHEC) D Enteropathogenic (EPEC) ANSWER: B Yersinia pestis, the causative agent of plague, is enzootic in the United States west of the 165 one-hundredth meridian. Human plague can be bubonic or pneumonic. The primary epidemiologic difference between the two clinical forms of plague is A Season of the year B Route of infection C Age of the patient D Health of the animal vector ANSWER: B A 9-year-old child is brought to the emergency room with the chief complaint of enlarged, painful axillary lymph nodes. The resident physician also notes a small, inflamed, dime-sized lesion surrounding what appears to be a small scratch on the 166 forearm. The lymph node is aspirated and some pus is sent to the laboratory for examination. A Warthin-Starry silver impregnation stain reveals many highly pleomorphic, rod-shaped bacteria. The most likely cause of this infection is A Y. pestis B Yersinia enterocolitica C Mycobacterium scrofulaceum D Bartonella henselae ANSWER: D Recently, there have been sensational media reports of patients infected with invasive, 167 “flesh-eating” bacteria that spread rapidly through the tissues. This necrotizing fasciitis is usually caused by A S. aureus B Group A streptococci C Micrococcus D Bacillus cereus ANSWER: B The most effective noninvasive test for the diagnosis of Helicobacterassociated gastric 168 ulcers is A Detection of H. pylori antigen in stool B Growth of H. pylori from a stomach biopsy C Growth of H. pylori in the stool D IgM antibodies to H. pylori ANSWER: A The following test results were observed in a woman tested in November who reported being in the woods in Pennsylvania during the past summer, was bitten by a tick, and now 169 has Bell’s palsy: Lyme IgG antibody 1:1280; Lyme IgM antibody negative. Which one of the following courses of action is most appropriate? Order tests for syphilis (VDRL, FTA-ABS) because there are cross-reactions reported A with Borrelia burgdorferi B Ask the patient if she has a severe headache C Consider treatment of the patient with an appropriate antibiotic such as tetra-cycline D Ask the patient if she has had a urinary tract infection with E. coli ANSWER: C Mycobacterium avium is a major opportunistic pathogen in AIDS patients. M. avium 170 from AIDS patients can be best characterized by which one of the following statements? A The majority of M. avium isolates from AIDS patients are nonpigmented B M. avium isolates from AIDS patients are of multiple serovars C Few isolates from AIDS patients are acid-fast D M. avium can be isolated from the blood of AIDS patients ANSWER: D Rheumatic fever (RF) is a disease seen in children and young adults. Which one of the 171 following statements best typifies the disease? It is characterized by inflammatory lesions that may involve the heart, joints, A subcutaneous tissues, and the central nervous system The pathogenesis is related to the similarity between a staphylococcal antigen and a B human cardiac antigen C Prophylaxis with benzathine penicillin is of little value D It is a complication of group A streptococcal skin disease but usually not of pharyngitis ANSWER: A If a quellung test was done on the following bacterial isolates, which one would you 172 expect to be positive? A S. pneumoniae B Enterobacter C Haemophilus parainfluenzae D C. diphtheriae ANSWER: A Bacteria cause disease in a number of ways. One mechanism of pathogenesis is the 173 secretion of potent protein toxins. All the following diseases are caused by microbial protein toxins, but one toxin has been used for a variety of maladies. It is A Tetanus B Botulism C Bacillary (Shigella) dysentery D Diphtheria ANSWER: B A 2-year-old child was admitted to the hospital with acute meningitis. The Gram stain 174 revealed Gram-positive short rods, and the mother indicated that the child had received “all” of the meningitis vaccinations. What is the most likely cause of the disease? A N. meningitidis, group A B N. meningitidis, group C C Listeria D S. pneumoniae ANSWER: C 175 The most common portal of entry for C. tetani, the cause of tetanus, is the A Skin B Gastrointestinal tract C Respiratory tract D Genital tract ANSWER: A 176 The most common way in which tuberculosis is acquired is via the A Skin B Gastrointestinal tract C Respiratory tract D Genital tract ANSWER: C Shigellosis is common in travelers to developing countries. Infection is commonly 177 acquired through the A Skin B Gastrointestinal tract C Respiratory tract D Genital tract ANSWER: B 178 A person who contracts gonorrhea is most likely to have acquired it via the A Skin B Gastrointestinal tract C Respiratory tract D Genital tract ANSWER: D There are a variety of “unusual” bacteria that infect humans. While rare, disease caused 179 by these microorganisms is serious and occasionally difficult to identify. Branhamella is best characterized as A A Gram-negative pleomorphic rod that can cause endocarditis B The causative agent of trench fever A Gram-negative rod, fusiforme-shaped, that is associated with periodontal disease but C may cause sepsis D The causative agent of sinusitis, bronchitis, and pneumonia ANSWER: D 180 Cardiobacterium is best characterized as A A Gram-negative pleomorphic rod that can cause endocarditis B The causative agent of trench fever A Gram-negative rod, fusiforme-shaped, that is associated with periodontal disease but C may cause sepsis D The causative agent of rat-bite fever ANSWER: A 181 Capnocytophyga is best characterized as A A Gram-negative pleomorphic rod that can cause endocarditis B The causative agent of trench fever A Gram-negative rod, fusiforme-shaped, that is associated with periodontal disease but C may cause sepsis D The causative agent of rat-bite fever ANSWER: C An enterococcus (E. faecium) was isolated from a urine specimen (100,000 cfu/mL). 182 Treatment of the patient with ampicillin and gentamicin failed. The most clinically appropriate action is A Do no further clinical workup B Suggest to the laboratory that low colony counts may reflect infection C Determine if fluorescent microscopy is available for the diagnosis of actinomycosis D Consider vancomycin as an alternative drug ANSWER: D A patient with symptoms of urinary tract infection had a culture taken, which grew 5 × 183 103 E. coli. The laboratory reported it as “insignificant.” The most clinically appropriate action is A Do no further clinical workup B Suggest to the laboratory that low colony counts may reflect infection C Determine if fluorescent microscopy is available for the diagnosis of actinomy-cosis D Consider vancomycin as an alternative drug ANSWER: B A patient appeared in the emergency room with a submandibular mass. A smear was 184 made of the drainage and a bewildering variety of bacteria were seen, including branched, Gram-positive rods. The most clinically appropriate action is A Do no further clinical workup B Suggest to the laboratory that low colony counts may reflect infection C Determine if fluorescent microscopy is available for the diagnosis of actinomy-cosis D Consider vancomycin as an alternative drug ANSWER: C 185 The antibiotic therapy of choice for legionellosis is A Penicillin B Ampicillin C Erythromycin D Vancomycin ANSWER: C 186 The antibiotic of choice for pneumococcal pneumonia is A Penicillin B Ampicillin C Erythromycin D Vancomycin ANSWER: A 187 The antibiotic of choice for streptococcal pharyngitis is A Penicillin B Ampicillin C Erythromycin D Vancomycin ANSWER: A 188 The therapy of choice for pseudomembranous enterocolitis is A Penicillin B Ampicillin C Erythromycin D Vancomycin ANSWER: D Although cholera, a Vibrio infection, has been rarely seen in the United States, there have been recent outbreaks of classic cholera associated with shellfish harvested from the Gulf 189 of Mexico. Vibrios are shaped like curved rods, and infections more common than cholera may be caused by a variety of curved-rod bacteria. C. jejuni is best described as “String-test”-positive isolate; three serotypes—Ogawa (AB), Inaba (AC), Hikojima A (ABC) B Human pathogen, halophilic, lactose-positive; produces heat-labile, extracellular toxin Human pathogen, halophilic, lactose-negative, sucrose-negative; causes gastrointestinal C diseases primarily from ingestion of cooked seafood D Cause of gastroenteritis; reservoir in birds and mammals, optimal growth at 42°C ANSWER: D Although cholera, a Vibrio infection, has been rarely seen in the United States, there have been recent outbreaks of classic cholera associated with shellfish harvested from the Gulf 190 of Mexico. Vibrios are shaped like curved rods, and infections more common than cholera may be caused by a variety of curved-rod bacteria. V. cholerae, the causative agent of cholera, is best described as “String-test”-positive isolate; three serotypes—Ogawa (AB), Inaba (AC), Hikojima A (ABC) B Human pathogen, halophilic, lactose-positive; produces heat-labile, extracellular toxin Human pathogen, halophilic, lactose-negative, sucrose-negative; causes gastrointestinal C diseases primarily from ingestion of cooked seafood D Cause of gastroenteritis; reservoir in birds and mammals, optimal growth at 42°C ANSWER: A Although cholera, a Vibrio infection, has been rarely seen in the United States, there have been recent outbreaks of classic cholera associated with shellfish harvested from the Gulf 191 of Mexico. Vibrios are shaped like curved rods, and infections more common than cholera may be caused by a variety of curved-rod bacteria. V. parahaemolyticus, first described in Japan, is best characterized as “String-test”-positive isolate; three serotypes—Ogawa (AB), Inaba (AC), Hikojima A (ABC) B Human pathogen, halophilic, lactose-positive; produces heat-labile, extracellular toxin Human pathogen, halophilic, lactose-negative, sucrose-negative; causes gastrointestinal C diseases primarily from ingestion of cooked seafood D Cause of gastroenteritis; reservoir in birds and mammals, optimal growth at 42°C ANSWER: C Although cholera, a Vibrio infection, has been rarely seen in the United States, there have been recent outbreaks of classic cholera associated with shellfish harvested from the Gulf of Mexico. Vibrios are shaped like curved rods, and infections more common than 192 cholera may be caused by a variety of curved-rod bacteria. Vibrio vulnificus, which can be found in the oceans and bays in temperate and tropical climates, is best characterized as “String-test”-positive isolate; three serotypes—Ogawa (AB), Inaba (AC), Hikojima A (ABC) B Human pathogen, halophilic, lactose-positive; produces heat-labile, extracellular toxin Human pathogen, halophilic, lactose-negative, sucrose-negative; causes gastrointestinal C diseases primarily from ingestion of cooked seafood D Cause of gastroenteritis; reservoir in birds and mammals, optimal growth at 42°C ANSWER: B Each bacterium listed below is a small, Gram-negative rod. Some of them are fastidious and may be difficult to culture and identify. They have unique microbiological features 193 and each of them causes distinctive clinical disease. Y. enterocolitica, formerly a Pasteurella, is best described by which of the following statements? Commonly inhabits the canine respiratory tract and is an occasional pathogen for A humans; strongly urease-positive Pits agar, grows both in carbon dioxide and under anaerobic conditions, and is part of the B normal oral cavity flora Typically infects cattle, requires 5 to 10% carbon dioxide for growth, and is inhibited by C the dye thionine Manifests different biochemical and physiologic characteristics, depending on growth D temperature, and causes a spectrum of human disease, most commonly mesenteric lymphadenitis ANSWER: D Each bacterium listed below is a small, Gram-negative rod. Some of them are fastidious and may be difficult to culture and identify. They have unique microbiological features 194 and each of them causes distinctive clinical disease. Brucella abortus, one of the three species causing brucellosis, a possible bioterrorism agent, is best described by which of the following statements? Commonly inhabits the canine respiratory tract and is an occasional pathogen for A humans; strongly urease-positive Pits agar, grows both in carbon dioxide and under anaerobic conditions, and is part of the B normal oral cavity flora Typically infects cattle, requires 5 to 10% carbon dioxide for growth, and is inhibited by C the dye thionine Typically is found in infected animal bites in humans and can cause hemorrhagic D septicemia in animals ANSWER: C Each bacterium listed below is a small, Gram-negative rod. Some of them are fastidious and may be difficult to culture and identify. They have unique microbiological features 195 and each of them causes distinctive clinical disease. Bordetella bronchiseptica could be confused with the agent of whooping cough. It is best described by which of the following statements? Commonly inhabits the canine respiratory tract and is an occasional pathogen for A humans; strongly urease-positive Pits agar, grows both in carbon dioxide and under anaerobic conditions, and is part of the B normal oral cavity flora Typically infects cattle, requires 5 to 10% carbon dioxide for growth, and is inhibited by C the dye thionine Typically is found in infected animal bites in humans and can cause hemorrhagic D septicemia in animals ANSWER: A Each bacterium listed below is a small, Gram-negative rod. Some of them are fastidious and may be difficult to culture and identify. They have unique microbiological features 196 and each of them causes distinctive clinical disease. P. multocida is a very common organism and is best described by which of the following statements? Commonly inhabits the canine respiratory tract and is an occasional pathogen for A humans; strongly urease-positive Pits agar, grows both in carbon dioxide and under anaerobic conditions, and is part of the B normal oral cavity flora Typically infects cattle, requires 5 to 10% carbon dioxide for growth, and is inhibited by C the dye thionine Typically is found in infected animal bites in humans and can cause hemorrhagic D septicemia in animals ANSWER: D To isolate specific bacteria from clinical specimens, it is necessary to use a variety of artificial media, some of which is selective, others of which are nonselective. N. 197 gonorrhoeae is a fastidious pathogen and found in sites often contaminated with normal flora. The best medium for isolation is A Sheep blood agar B Löffler’s medium C Thayer-Martin agar D Thiosulfate citrate bile salts sucrose medium ANSWER: C To isolate specific bacteria from clinical specimens, it is necessary to use a variety of 198 artificial media, some of which is selective, others of which are nonselective. V. cholerae, the causative agent of cholera, is best isolated using A Sheep blood agar B Löffler’s medium C Thayer-Martin agar D Thiosulfate citrate bile salts sucrose medium ANSWER: D To isolate specific bacteria from clinical specimens, it is necessary to use a variety of artificial media, some of which is selective, others of which are nonselective. M. 199 tuberculosis can be found in the sputum of patients with tuberculosis. After digestion of the sputum, isolation is best accomplished using A Sheep blood agar B Löffler’s medium C Thayer-Martin agar D Löwenstein-Jensen medium ANSWER: D To isolate specific bacteria from clinical specimens, it is necessary to use a variety of artificial media, some of which is selective, others of which are nonselective. C. 200 diphtheriae may be difficult to isolate from the nasopharynx without the use of special media. The medium of choice is A Sheep blood agar B Löffler’s medium C Thayer-Martin agar D Thiosulfate citrate bile salts sucrose medium ANSWER: B To isolate specific bacteria from clinical specimens, it is necessary to use a variety of 201 artificial media, some of which is selective, others of which are nonselective. S. aureus has a distinctive appearance on which one of the following media? A Sheep blood agar B Löffler’s medium C Thayer-Martin agar D Thiosulfate citrate bile salts sucrose medium ANSWER: A In order to recognize abnormal bacteria, it is necessary to know which bacteria are 202 predominant normal flora of certain body sites. Which of the following is the predominant organism on skin commonly seen as a blood culture contaminant? A α-hemolytic streptococci B Lactobacillus C S. epidermidis D Escherichia coli ANSWER: C In order to recognize abnormal bacteria, it is necessary to know which bacteria are 203 predominant normal flora of certain body sites. Which of the following is the predominant flora of the mouth that is the major cause of dental caries? A α-hemolytic streptococci B Lactobacillus C S. epidermidis D E. coli ANSWER: A In order to recognize abnormal bacteria, it is necessary to know which bacteria are 204 predominant normal flora of certain body sites. Which of the following is the most prevalent microorganism in the vagina that may also be protective? A α-hemolytic streptococci B Lactobacillus C S. epidermidis D E. coli ANSWER: B 205 Streptococcus mutans is best described as A facultative anaerobe that often inhabits the buccal mucosa early in a neonate’s life and A can cause bacterial endocarditis B A β-hemolytic organism that causes a diffuse, rapidly spreading cellulitis C An anaerobic, filamentous bacterium that often causes cervicofacial osteomyelitis A facultative anaerobe that is highly cariogenic and sticks to teeth by synthesis of a D dextran ANSWER: D 206 Streptococcus salivarius, a common isolate in the clinical laboratory, is best described as A facultative anaerobe that often inhabits the buccal mucosa early in a neonate’s life and A can cause bacterial endocarditis B A β-hemolytic organism that causes a diffuse, rapidly spreading cellulitis C An anaerobic, filamentous bacterium that often causes cervicofacial osteomyelitis A facultative anaerobe that is highly cariogenic and sticks to teeth by synthesis of a D dextran ANSWER: A 207 A. israelii is one of many actinomycetes and is best described as A facultative anaerobe that often inhabits the buccal mucosa early in a neonate’s life and A can cause bacterial endocarditis B A β-hemolytic organism that causes a diffuse, rapidly spreading cellulitis C An anaerobic, filamentous bacterium that often causes cervicofacial osteomyelitis A facultative anaerobe that is highly cariogenic and sticks to teeth by synthesis of a D dextran ANSWER: C 208 A. viscosus, another ubiquitous actinomycete, can best be described as A facultative anaerobe that often inhabits the buccal mucosa early in a neonate’s life and A can cause bacterial endocarditis B A β-hemolytic organism that causes a diffuse, rapidly spreading cellulitis C An anaerobic, filamentous bacterium that often causes cervicofacial osteomyelitis D A facultatively anaerobic, rod-shaped bacterium that sticks to teeth and is cariogenic ANSWER: D Diphtheriae causes diphtheria, a rare disease in the United States. diphtheriae is best 209 characterized by which of the following statements? A It secretes erythrogenic toxin that causes the characteristic signs of scarlet fever It produces toxin that blocks protein synthesis in an infected cell and carries a lytic B bacteriophage that produces the genetic information for toxin production It produces at least one protein toxin consisting of two subunits, A and B, that cause C severe spasmodic cough usually in children D It requires cysteine for growth ANSWER: B Bordetella pertussis is a Gram-negative rod that causes severe respiratory disease. Which 210 one of the following statements best characterizes this microorganism? A It secretes erythrogenic toxin that causes the characteristic signs of scarlet fever It produces toxin that blocks protein synthesis in an infected cell and carries a lytic B bacteriophage that produces the genetic information for toxin production It produces at least one protein toxin consisting of two subunits, A and B, that cause C severe spasmodic cough usually in children D It requires cysteine for growth ANSWER: C Francisella tularensis is the bacterium that causes tularemia, a disease not uncommonly 211 seen in hunters. Which one of the following statements best characterizes this bacterium? A It secretes erythrogenic toxin that causes the characteristic signs of scarlet fever It produces toxin that blocks protein synthesis in an infected cell and carries a lytic B bacteriophage that produces the genetic information for toxin production It produces at least one protein toxin consisting of two subunits, A and B, that cause C severe spasmodic cough usually in children D It requires cysteine for growth ANSWER: D E. coli 0157/H7 is a newsworthy microorganism that has been isolated from foods (meat) 212 and beverages (cider) with increasing frequency. Its characteristic biology is best described by which of the following statements? A It secretes erythrogenic toxin that causes the characteristic signs of scarlet fever It produces toxin that blocks protein synthesis in an infected cell and carries a lytic B bacteriophage that produces the genetic information for toxin production It produces at least one protein toxin consisting of two subunits, A and B, that cause C severe spasmodic cough usually in children It secretes exotoxin that has been called “verotoxin” and “Shiga-like toxin”; infection is D mediated by specific attachment to mucosal membranes ANSWER: D Streptococcus pyogenes is a toxigenic bacterium causing a variety of diseases. Which of 213 the following statements best characterizes this organism? A It secretes erythrogenic toxin that causes the characteristic signs of scarlet fever It produces toxin that blocks protein synthesis in an infected cell and carries a lytic B bacteriophage that produces the genetic information for toxin production It produces at least one protein toxin consisting of two subunits, A and B, that cause C severe spasmodic cough usually in children D It requires cysteine for growth ANSWER: A N. meningitidis causes meningitis in all age groups. A characteristic physiological trait is 214 that it Possesses N-acetylneuraminic acid capsule and adheres to specific tissues by pili found A on the bacterial cell surface B Has capsule of polyglutamic acid, which is toxic when injected into rabbits C Synthesizes protein toxin as a result of colonization of vaginal tampons Causes spontaneous abortion and has tropism for placental tissue due to the presence of D erythritol in allantoic and amniotic fluid ANSWER: A Brucella is pathogenic for humans and animals. Which one of the following statements 215 best characterizes this organism? A It has capsule of polyglutamic acid, which is toxic when injected into rabbits B It synthesizes protein toxin as a result of colonization of vaginal tampons It causes spontaneous abortion and has tropism for placental tissue due to the presence of C erythritol in allantoic and amniotic fluid D It secretes two toxins, A and B, in large bowel during antibiotic therapy ANSWER: C An 18-year-old male patient appeared at the emergency room with a 3-day history of fever, dry cough, difficulty breathing, and muscle aches and pains. His chest x-ray showed a diffuse left upper lobe infiltrate. The following 5 questions focus on the 216 etiology of “atypical” or communityacquired pneumonia: Mycoplasma pneumoniae pneumonia (walking pneumonia) may be rapidly identified by which of the following procedures? A Detection of specific antigen in urine B Cold agglutinin test C Electron microscopy of sputum D Culture of respiratory secretions in HeLa cells after centrifugation of the inoculated tubes ANSWER: D An 18-year-old male patient appeared at the emergency room with a 3-day history of fever, dry cough, difficulty breathing, and muscle aches and pains. His chest x-ray showed a diffuse left upper lobe infiltrate. The following 5 questions focus on the 217 etiology of “atypical” or communityacquired pneumonia: Influenza can be treated; therefore, specific detection of the virus becomes much more important. Which of the following would be best for detection of influenza? A Detection of specific antigen in urine B Cold agglutinin test C Electron microscopy of sputum D Detection of antigen in respiratory secretions ANSWER: A Legionnaires’ disease is most rapidly diagnosed by which one of the following 218 procedures? A Detection of specific antigen in urine B Cold agglutinin test C Electron microscopy of sputum D Detection of antigen in respiratory secretions ANSWER: D An 18-year-old male patient appeared at the emergency room with a 3-day history of fever, dry cough, difficulty breathing, and muscle aches and pains. His chest x-ray showed a diffuse left upper lobe infiltrate. The following 5 questions focus on the 219 etiology of “atypical” or communityacquired pneumonia: Chlamydia pneumoniae has recently been implicated in respiratory disease primarily in children. Which of the following would best isolate this fastidious bacterium? A Detection of specific antigen in urine B Cold agglutinin test C Electron microscopy of sputum D Culture of respiratory secretions in HeLa cells after centrifugation of the inoculated tubes ANSWER: D An 18-year-old male patient appeared at the emergency room with a 3-day history of fever, dry cough, difficulty breathing, and muscle aches and pains. His chest x-ray showed a diffuse left upper lobe infiltrate. The following 5 questions focus on the 220 etiology of “atypical” or communityacquired pneumonia: Bordetella bronchitis, sometimes called whooping cough, can best be detected by which of the following procedures? A Fluorescent antibody detection of the organism in sputum B Cold agglutinin test C Direct microscopy of sputum by Gram stain D Culture of respiratory secretions on Regan-Lowe agar ANSWER: D 221 Which of the following bacterial transport methods is energyindependent? A Facilitated diffusion B Simple diffusion C Proton gradient energized active transport D Group translocation ANSWER: B Iron is essential in bacterial metabolism. When bacteria invade the human host they must 222 capture iron in order to survive. Which of the macromolecules listed below is important in bacterial iron metabolism? A Transferrin B Lactoferrin C Ferric oxide D Siderophores ANSWER: D An aliquot of Escherichia coli is treated with ethylenediaminetetraacetic acid (EDTA). The first wash is analyzed and found to contain alkaline phosphatase, DNase, and 223 penicillinase. The anatomic area of the cell affected by the EDTA is most likely to have been the A Periplasmic space B Mesosomal space C Chromosome D Plasma membrane ANSWER: A A bacterium is examined and is found to lack superoxide dismutase, catalase, and 224 peroxidase. Which of the following statements best describes this bacterium? A This bacterium is an anaerobe B This bacterium will survive in an O2 environment C This bacterium is more virulent than one containing the three enzymes D This bacterium does not produce superoxide ANSWER: A Analysis of the metabolites produced by an organism’s fermentation of glucose reveals 225 small amounts of 6-phosphogluconic acid. This fermentation organism is most likely to be A Enterobacter B Escherichia C Leuconostoc D Enterococcus faecalis ANSWER: C The formation of adenosine triphosphate (ATP) is essential for the maintenance of life. In mammalian systems, the number of moles of ATP formed per gram atom of oxygen 226 consumed (the P/O ratio) is 3; in bacteria, however, the P/O ratio may be only 1 or 2. The primary reason for the lower P/O ratio in bacteria is A Absence of nicotinamide adenine dinucleotide (NAD) B Loss of oxidative phosphorylation coupling sites C Less dependence on ATP as an energy source D Absence of a nonphosphorylative bypass reaction ANSWER: B Reversion of Neisseria gonorrhoeae from a fimbriated (fim 1) to a nonfimbriated (fim 2) 227 state would result in which one of the following phenomena? A Inability of N. gonorrhoeae to colonize the mucosal epithelium B Reversion to a Gram-positive stain C Death of the organism D Loss of serologic specificity ANSWER: A An unknown isolate is recognized serologically as Salmonella enteritidis serovar 228 newport. A mutant of this organism has lost region 1 (O-specific polysaccharide) of its lipopolysaccharide. This mutant would be identified as A Salmonella typhi B Salmonella newport C S. enteritidis D S. enteritidis serovar newport ANSWER: C Certain enzymes catalyze the cross-linking of peptidoglycan, a unique constituent of 229 bacterial cell walls. Which of the following may be a factor in antibiotic resistance, the target of which is cell-wall synthesis? A Bactoprenol B Reverse transcriptase C RNA polymerase D Penicillin-binding proteins (PBPs) ANSWER: D Ideally, an antibiotic should focus on a microbial target not found in mammalian cells. By 230 this standard, which of the following antibiotic agents would be expected to be most toxic to humans? A Penicillin B Mitomycin C Cephalosporin D Bacitracin ANSWER: B 231 E. coli has two major porins located in the outer membrane. The function of porins is the A Stabilization of the mesosome B Metabolism of phosphorylated intermediates C Transfer of small molecules through the outer membrane D Serologic stabilization of the O antigen ANSWER: C Early attempts at the polymerase chain reaction (PCR) used E. coli DNA polymerase. 232 This was replaced with DNA polymerase from Thermus aquaticus (“Taq” polymerase). The primary advantage in using this enzyme is A It is cheaper than E. coli polymerase B Specificity is increased because nonspecific hybridization of primers does not occur C Use of Taq polymerase results in fewer PCR cycles D Use of Taq polymerase enables lower temperatures to be used ANSWER: B You have been asked to design a nucleic acid amplification test for a rarely isolated bacterium. There are several questions that you must ask in order to develop a test that 233 could be used to diagnose disease. Assume, initially, that the polymerase chain reaction (PCR) will amplify any DNA, human or microbial. The best way to prevent contamination of the PCR process is to A Wear gloves B Wash benches with bleach C Use universal precautions D Incorporate self-sterilizing agents into the PCR mixture ANSWER: D You have been asked to design a nucleic acid amplification test for a rarely isolated bacterium. There are several questions that you must ask in order to develop a test that could be used to diagnose disease. You must choose primers for this PCR. Primers are 234 small pieces of nucleic acid that recognize a pair of unique sites on the bacterial chromosome. For an optimum test to be developed, which of the following characteristics is the least desirable? A Ability to be constructed by a synthesizer B Uniqueness to the organism that you wish to detect C Complementary to sequences on the bacterial chromosome D That the sequences are widely recognized by many bacterial species ANSWER: D You have been asked to design a nucleic acid amplification test for a rarely isolated bacterium. There are several questions that you must ask in order to develop a test that could be used to diagnose disease. You have chosen the primers for the PCR that you 235 have designed. You have also developed a reaction mixture that contains, among other substances, a polymerase enzyme. After the primer pairs have been amplified, they must be detected. Which of the following detection methods is most sensitive (that is, will detect the highest number of amplicons)? A Southern blot B Ethidium staining of the amplified products (amplicons) C Microscopy D Capture of the amplicons on a solid phase followed by an enzyme immuno-assay ANSWER: A The purpose of gene cloning is to produce large amounts of genes in pure form. The 236 sequence of the cloning process is critical to the production of clones. Which of the following steps initializes the cloning process? A Isolation and fragmentation of source DNA B Amplification of source DNA C Detection and purification of clones D Joining of host DNA to a cloning vector ANSWER: A Nucleic acid probes are not only useful for searching for genes in the cloning host but 237 also for searching for genes or gene fragments in patient specimens. Which one of the following statements is true of nucleic acid probes? A Only DNA can be used as a probe B Primers are labeled to allow detection, but probes are unlabeled Nucleic acid probes are not as sensitive as traditional culture methods for detection of C pathogenic microorganisms Probes can be designed so that they can detect very specific pieces of a nucleic acid, for D example, a penicillin-resistant gene ANSWER: D DNA from a host sample can be amplified by a process known as the polymerase chain 238 reaction (PCR). Which of the following is required for PCR? A Knowledge of the genetic sequence to be amplified B An single nucleotide primer C An ultracentrifuge D A universal probe to detect the amplified product ANSWER: A DNA can be transferred from one bacterium to another by a number of processes. Uptake 239 by a recipient cell of soluble DNA released from a donor cell is defined as A Conjugation B Recombination C Competence D Transformation ANSWER: D DNA can be transferred from one bacterium to another by a number of processes. 240 Transfer of a donor chromosome fragment by a temperate bacterial virus is defined as A Conjugation B Recombination C Competence D Transduction ANSWER: D DNA can be transferred from one bacterium to another by a number of processes. Direct 241 transfer of a plasmid between two bacteria is defined as A Conjugation B Recombination C Competence D Transformation ANSWER: A 242 A broad-spectrum antibiotic in the general class of thienamycins is A Piperacillin B Cefoperazone C Ceftriaxone D Imipenem ANSWER: D 243 Third-generation cephalosporin with good activity against Borrelia burgdorferi is A Piperacillin B Cefoperazone C Ceftriaxone D Ciprofloxacin ANSWER: C 244 Broad-spectrum penicillin with antipseudomonas activity is A Piperacillin B Cefoperazone C Ceftriaxone D Ciprofloxacin ANSWER: A 245 Third-generation cephalosporin with primary activity against Pseudomonas aeruginosa is A Piperacillin B Cefoperazone C Ceftriaxone D Ciprofloxacin ANSWER: B 246 Quinolone antibiotic with broad Gram-negative and Gram-positive activity is A Piperacillin B Cefoperazone C Ceftriaxone D Ciprofloxacin ANSWER: D 247 Which one of the following antibiotics inhibits dihydrofolate reductase? A Penicillin B Amdinocillin C Amphotericin D Trimethoprim ANSWER: D 248 Which one of the following antibiotics binds to penicillin-binding protein-2 (PBP-2)? A Penicillin B Amdinocillin C Amphotericin D Chloramphenicol ANSWER: B Which one of the following antibiotics inhibits the final peptide bond between d-alanine 249 and glycine? A Penicillin B Amdinocillin C Amphotericin D Chloramphenicol ANSWER: A 250 Which one of the following antibiotics binds sterols and alters membrane permeability? A Penicillin B Amdinocillin C Amphotericin D Chloramphenicol ANSWER: C Which one of the following antibiotics attaches to 50S ribosome and inhibits peptidyl 251 transferase? A Penicillin B Amdinocillin C Amphotericin D Chloramphenicol ANSWER: D Bacteria or their components may be characterized by unique constituents or structures. 252 Bacterial lipopolysaccharide (LPS) is characterized by A Phospholipid B Ribitol teichoic acid C Gly