Microbiology Question Bank Exam 2020/2021 PDF

Microbiology Question Bank Exam 2020/2021 1. All of the following agents have good ac vity against Gram posi ve organisms except: a. aztreonam b. daptomycin c. tigecyclin d. quinupristin-dalfopristin 2. Each of the following statements regarding...

Microbiology Question Bank Exam 2020/2021 1. All of the following agents have good ac vity against Gram posi ve organisms except: a. aztreonam b. daptomycin c. tigecyclin d. quinupristin-dalfopristin 2. Each of the following statements regarding bacterial taxonomy is correct EXCEPT a. Numerical taxonomy is based on computerized numerical comparisons of large number of characteristics b. Phylogenetic taxonomy is based on the determination of DNA relatedness between a given strain and every known species. c. bacterial strain is basic taxonomic groups d.) Bacterial species is a group of organisms that resemble one another closely in the most important features of their organization 3. Regarding Shigella and Campylobacter, which one of the following is LEAST accurate ???? a. Both have an animal reservoir that acts as a source of infection for humans. b. Both can be cultured on bacteriologic media in the clinical laboratory. c. Both typically cause white blood cells to appear in the stool. d. Both are gram-negative rods. 4. 65-year-old man develops dysuria and hematuria. A Gram stain of urine sample shows gram-nega ve rods. Culture of the urine on EMB agar reveals lactose- nega ve colonies without evidence of swarming mo lity. Which one of the following organisms is MOST likely to be the cause of his urinary tract infec on? Select one: a. Enterococcus faecalis b. Proteus vulgaris c. Staphylococcus aureus d. Pseudomonas aeruginosa 5. Each of the following statements about staphylococci is correct EXCEPT Select one: a. Some strains of S. аureus are resistant to penicillin due to production of b–lactamase. b. Some strains of S. аureus cause rheumatic fever as a result of an immunologic cross- reaction between the proteins of the organism and proteins of the myocardium. c. Some strains of S. аureus produce an exotoxin which is an enterotoxin that causes vomiting and diarrhea. d. Staphylococcus aureus produces coagulase, whereas Staphyloccus epidermidis does not. ti ti ti ti ti ti  6. Each of the following statements regarding Cryptococcus neoformans is correct EXCEPT Select one: a. Diagnosis of cryptococcal disease can be made by detecting the polysaccharide capsular antigen in body fluids, e.g., spinal fluid. b. It is a dimorphic fungus that forms septate hyphae in the soil and yeasts in the infected individual. c. It is typically acquired by inhalation, and primary infections occur in the lungs. d. It causes disseminated disease, e.g., meningitis, more often in immunocompromised individuals than in the immunocompetent. 7. Measles virus and rubella virus share several features. Which one of the following is LEAST accurate ???? Select one: a. They both induce lifelong immunity following natural infection. b. They are both enveloped RNA viruses. c. They are both a significant cause of congenital abnormalities. d. They are both transmitted by respiratory aerosol and cause diseases characterized by a skin rash 8. Each of the following statements concerning spirochetes is correct EXCEPT Select one: a. The species of Leptospira that causes leptospirosis grows primarily in humans and are usually transmitted by human-to-human contact. b. Species of Borrelia cause a tick-borne disease called relapsing fever. c. Species of Treponema cause syphilis and yaws. d. Species of Treponema are part of the normal flora of the mouth. 9. Which one of the following phrases accurately describes viral neutralizing an bodies? Select one: a. Directed against viral nucleic acid sequences. b. Appear in the host sooner after viral infection than interferon. c. Induced only by disease-causing viruses. d. Of little importance to immunity to viral infection. e. Directed against viral protein on the outside of the virus particle. ti  10. Each of the following statements concerning Mycobacterium leprae is correct EXCEPT Select one: a. The organism will grow on bacteriologic media in 3-6 weeks. b. The incubation period of leprosy is probably 2-10 years. c. Prolonged therapy (9 months or longer) is required to prevent recurrence. d. In lepromatous leprosy, large numbers of organisms are usually seen in acid-fast stained smears 11. A woman who is HBsAg posi ve and HBsAb nega ve has just given birth. Which one of the following is the most appropriate thing to do for the newborn? Select one: a. Give both the HBV vaccine and HBIG. b. Immunize with the vaccine containing HBsAg (HBV vaccine). c. Nothing. The child is protected against hepatitis B. d. Give hepatitis B hyperimmune globulins (HBIG). 12. A delayed hypersensi vity reac on is characterized by Select one: a. an infiltrate composed of eosinophils b. an infiltrate composed of neutrophils c. an infiltrate composed of lymphocytes and macrophages d. edema without a cellular infiltrate 13. Each of the following statements regarding bacterial granules is correct EXCEPT ???? Select one: a. They can be composed of glycogen, lipids, polyphosphates. b. Acid-fast stain is the stain of choice for identifying the metachromatic granules. c. They are not essential structures. d. Polyphosphates (volutin or metachromatic) granules in Corynebacteria serve as a diagnostic criterion. 14. Each of the following statements concerning Clostridium Tetani is correct EXCEPT Select one: a. Pathogenesis is due to the production of an exotoxin that blocks inhibitory neurotransmitters. b. It is a gram-positive, spore-forming rod. c. It will grow on a blood agar plate in the presence of room air. d. It's natural habitat is primarily the soil. 15. Each of the following statements concerning retrovirus is correct EXCEPT Select one: ti ti ti ti  a. During infection, the virus synthesizes a DNA copy of its RNA, and this DNA becomes covalently integrated into host cell DNA. b. The virus particle carries an RNA-directed DNA polymerase encoded by the viral genome. c. The viral genome consists of 3 segments of double-stranded DNA. d. The virion is enveloped and enters cells via an interaction with specific receptors on the host cell. 16. Each of the following statements regarding bacterial endotoxin is correct EXCEPT Select one: a. Endotoxin is a lipopolysaccharide, the lipid portion of which mediates the toxicity. b. Endotoxin causes hypotension by catalyzing the addition of ADP-ribose to the alpha chain of T cell receptors. c. Endotoxin causes fever by inducing interleukin-1 production by macrophages. d. Both gram-negative rods and gram-negative cocci have endotoxin. 17. Which one of the following groups of an microbial agents acts on microorganisms by inhibi ng protein synthesis? Select one: a. Fluoroquinolones b. Aminoglycosides c. Polymyxins d. Glycopeptides (eg, vancomycin) e. Penicillins 18. Each of the following statements regarding poststreptococcal nonsupura ve complica ons is correct EXCEPT Select one: a. Both acute rheumatic fever and acute glomerulonephritis are preceded by Streptococcus pyogenes infection. b. Rheumatic fever occurs when an immune response against streptococcal antigens cross- reacts with cardiac muscle and with joint cartilage. c. Patients with rheumatic fever typically have a high titer of antibody to streptolysin O (a hemolysin). d. Glomerulonephritis occurs when streptococci infect the nephrons and release catalase, which causes disruption of the glomerular membrane and loss of protein in the urine. ti ti ti ti  19. Each of the following statements concerning pneumonia caused by Mycoplasma pneumoniae is correct EXCEPT Select one: a. The disease is one of the “atypical” pneumonias. b. The disease occurs primarily in immunocompetent individuals. c. The organism cannot be cultured in vitro since it has no cell wall. d. The disease is associated with a rise in the titer of cold agglutinins. 20. Which one of the following is NOT a characteris c of the staphylococcus associated with toxic shock syndrome? Select one: a. Appearance of the organism in grapelike clusters on Gram-stained smear. b. Catalase-negative reaction. c. Elaboration of enterotoxin F. d. Coagulase production. 21. Which one of the following viruses that causes human diseases has an animal reservoir? Select one: a. Yellow fever virus b. Cytomegalovirus c. Hepatitis C virus d. Varicella-zoster virus 22. The Bacterial chromosome is best described as ???? Select one: a. a large circular strand of double-stranded DNA surrounded by the membrane b. a large circular strand of supercoiled double-stranded DNA c. fragmented pieces of double-stranded DNA d. a large strand of single-stranded RNA 23. In the Gram stain, the decoloriza on of Gram-nega ve bacteria by alcohol is MOST closely related to Select one: a. branched polysaccharides in the capsule b. lipids in the cell wall c. 70S ribosomes d. proteins encoded by F plasmids 24. Each of the following statements regarding pep doglycan is correct EXCEPT ???? Select one: ti ti ti ti a. Peptidoglycan is a unique feature of the prokaryotic cells. b. The peptidoglycan is a good target for antimicrobial agents. c. It consists of a glycan backbone (of repeating N-acetylmuramic acid and N- acetylglucosamine molecules) tetrapeptide side chains and peptide cross-bridges between the two tetrapeptides. d. The enzyme catalase can cleave the peptidoglycan backbone by breaking its glycoside bonds. 25. All of the following are true statements about lysogens EXCEPT ???? Select one: a. phage DNA can be covalently joined with the bacterial DNA b. phage repressor protects the bacteria from subsequent infections by all types of phage c. lytic functions are not expressed d. phage DNA can exist in the bacterial cytoplasm 26. Each of the following statements regarding the capsules of bacteria is correct EXCEPT Select one: a. Bacterial capsules can be purified and used in vaccines against certain bacteria, e.g., the pneumococcus. b. Most bacterial capsules are antigenic. This antigenicity can vary. If the antigenicity varies, the bacteria have many different serologic types (serotypes). c. Most bacterial capsules are polysaccharides and serve to protect the bacteria by inhibiting phagocytosis. d. Most gram-positive bacteria have capsules, whereas gram-negatives rarely do. 27. Each of the following statements regarding herpes simplex virus type 2 is correct EXCEPT ???? Select one: a. It is an important cause of encephalitis in adults. b. It is an important cause of neonatal infection. c. Painful vesicular lesions occur on the genitals of both men and women. d. Acyclovir can be used to treat primarily lesions in an immunocompetent host. 28. Which one of the following states a principle regarding viral nucleic acid? Select one: a. Viral genome sizes are similar among known human viruses.  b. Some viruses contain a segmented genome. c. Viruses contain both RNA and DNA. d. Purified viral nucleic acid from any virus is usually infectious. 29. Each of the following statements concerning exotoxins is correct EXCEPT Select one: a. Botulism is caused by a toxin that hydrolyzes lecithin (lecithinase), thereby destroying nerve cells. b. Diphtheria is caused by an exotoxin that inhibits protein synthesis by inactivating an elongation factor. c. Cholera toxin acts by stimulating adenylate cyclase. d. Some strains of Escherichia coli produce an enterotoxin that causes diarrhea. 30. Which one of the following is NOT an important characteris c of Streptococcus pyogenes? Select one: a. Beta-hemolysin b. M protein c. Protein A d. Polysaccharide group-specific substance 31. Microorganisms that can grow best at low O2 concentra ons and can also grow without O2 are called: Select one: a. aerobes b. strict anaerobes c. facultative anaerobes d. microaerophilic 32. Which of the following organisms causes diarrhea by producing an enterotoxin that ac vates adenylate cyclase? Select one: a. Escherichia coli b. Bacteroides fragilis c. Streptococcus faecalis d. Staphylococcus aureus 33. Each of the following statements concerning arboviruses is correct EXCEPT Select one: ti ti ti a. Wild birds are the reservoir for encephalitis viruses but not for yellow fever virus. b. The pathogenesis of dengue hemorrhagic shock syndrome is associated with the heterotypic anamnestic response. c. Ticks are the main mode of transmission for both encephalitis viruses and yellow fever virus. d. There is a live, attenuated vaccine that effectively prevents yellow fever. 34. Which one of the following illnesses is NOT a zoonosis? Select one: a. Q fever b. Anthrax c. Tularemia d. Typhoid fever 35. Each of the following statements concerning Neisseria is correct EXCEPT Select one: a. They are gram-negative diplococci. b. They are oxidase-positive. c. They produce IgA protease as a virulence factor. d. They grow best under anaerobic conditions 36. The helper T: suppressor T cell ra o in AIDS is Select one: a. lower than normal because viral replication destroys helper T cells b. higher than normal because viral replication destroys suppressor T cells c. higher than normal because viral replication stimulates helper T cell growth d. lower than normal because viral replication stimulates macrophage growth 37. Each of the following statements concerning Mycobacterium tuberculosis is correct EXCEPT Select one: a. M. tuberculosis appears as a red rod in acid-fast stained specimens. b. M. tuberculosis has a large amount of mycolic acid in its cell wall. c. M. tuberculosis appears as a red rod in Gram-stained specimens. d. After being stained with carbolfuchsin, M. tuberculosis resists decolorization with acid alcohol. ti  38. Each of the following statements regarding Borrelia burgdorferi is correct EXCEPT Select one: a. Infections are typically diagnosed serologically. b. It is transmitted from the animal reservoir to humans by tick bite. c. It is the causative agent of Lyme disease. d. It is a gram-positive rod that is divided into 4 serotypes on the basis of its capsular polysaccharide. 39. Which of the following statements regarding virus morphology is true? Select one: a. Viral surface proteins protect the viral genome from nucleases. b. All RNA viruses are spherical in shape. c. Helical nucleocapsids are found with single-stranded DNA viruses. d. Some viruses with DNA genomes contain a primitive nucleus. e. Some viruses contain flagella. 40. Phage conversion is responsible for the produc on of some toxins of all the following bacteria EXCEPT ???? Select one: a. Staphylococcus aureus (a food enterotoxin) b. Corynebacterium diphtheriae (diphtheria toxin) c. Bacteroides fragilis (fragilinum toxin) ? d. Clostridium botulinum (botulinum toxin) 41. Regarding in uenza virus and the disease in uenza, which one of the following statements is most accurate? Select one: a. Influenza A virus causes more severe disease and more widespread epidemics than does influenza B virus. b. Chronic carriers (i.e., patients from whom influenza virus is isolated at least 6 months after the acute disease) are an importanst source of human infection. c. Both the killed and the live, attenuated vaccines induce lifelong immunity. d. The genom of Influenza A virus has eight segments, but the genome of influenza B virus is in one piece. e. The classification of influenza viruses into A,B and C viruses is based on antigenic differences in their hemagglutinin. fl fl ti  42. Which one of the following statements regarding Treponema pallidum is MOST accurate? Select one: a. Since the lesions of primary syphilis are primarily due to an immune response against the organism, the lesions typically contain a few T. pallidum cells. b. It is a spiral-shaped rod that appears gram-positive in Gram-stained smears. c. Treatment consist of prolonged administration of penicillin G. d. Specimens cultured on blood agar plates reveal alpha-hemolytic colonies. 43. Each of the following statements concerning gonorrhoea is correct EXCEPT Select one: a. Gonococcal conjunctivitis of the newborn rarely occurs, because silver nitrate or erythromycin is commonly used as prophylaxis. b. A presumptive diagnosis can be made by finding gram-negative kidney-bean-shaped diplococci within neutrophils in a urethral discharge. c. Piliated gonococci are usually avirulent whereas nonpiliated strains are virulent. d. Infection in men is more frequently symptomatic than in women. 44. Which of the following viruses causes a mononucleosis-like syndrome and is excreted in the urine? Select one: a. Human herpesvirus 6 b. Epstein-Bar virus c. Varicella-zoster virus d. Cytomegalovirus e. Herpes simplex virus type 2 45. Each of the following statements regarding bacterial metabolism is correct EXCEPT Select one: a. The oxidative pentose phosphate pathway exists concomitantly with either the glycolytic pathway or the Entner-Doudroff pathway. b. The Entner-Doudroff pathway is found in obligate aerobes. c. The glycolytic pathway is found only in obligate anaerobes. d. Pyruvate is the terminal product from glucose dissimilation.  46. The regula on of enzyme ac vity provides ne control of metabolic pathways. Which of the following regulatory mechanisms provides ne control of a biosynthe c pathway? Select one: a. Feedback inhibition b. None of the above c. Induction d. Attenuation e. Catabolite repression 47. The pathogenesis of which one of the following organisms is MOST likely to involve invasion of the intes nal mucosa? Select one: a. Enterotoxigenic Escherichia coli b. Clostridium botulinum c. Vibrio cholerae d. Shigella sonnei 48. Each of the following statements concerning the resistance of bacteria to an microbial drugs is correct EXCEPT Select one: a. Resistance to penicillin is known to be due to reduced affinity of transpeptidases. b. Resistance to penicillin is known to be due to cleavage by ß-lactamase. c. Resistance to chloramphenicol is known to be due to an enzyme that acetylates the drug. d. Resistance to tetracycline is known to be due to an enzyme that hydrolyzes the ester linkage. 49. A 74-year-old man develops fever, malaise, and a sore throat followed shortly by nausea, vomi ng, and then stupor. Eastern equine encephali s is diagnosed. Control of this disease in humans could be accomplished by eradica on of which of the following? Select one: a. Horses ti ti ti tti ti ti fi fi ti ti  b. Ticks c. Mosquitoes d. Sandflies 50. Each of the following statements regarding bacterial taxonomy is correct EXCEPT Select one: a. Numerical taxonomy is based on computerized numerical comparisons of large number of characteristics. b. Bacterial species is a group of organisms that resemble one another closely in the most important features of their organisation. c. Bacterial strain is the basic taxonomic group. d. Phylogenetic taxonomy is based on the determination of DNA relatedness between a given strain and every known species. 51. Regarding the nature of medically important viruses, which one of the following statements is LEAST accurate? Select one: a. Poliovirus is a nonenveloped virus with RNA as its genome. b. Influenza virus is an enveloped virus with RNA as its genome. c. Hepatitis B virus is an enveloped virus with DNA as its genome. d. Epstein-Barr virus is a nonenveloped virus with RNA as its genome. 52. The drug of rst choice for the treatment of serious anaerobic infec ons caused by B. fragilis is: Select one: a. Ampicillin b. Metronidazole c. Amoxicillin–clavulanate d. Cefoxitin e. Clindamycin 53. Five hours a er ea ng fried rice at a restaurant, a 24-year-old woman and her husband both developed nausea, vomi ng, and diarrhea. Which one of the following organisms is the MOST likely to be involved? ft fi ti ti ti  Select one: a. Bacillus cereus b. Enterotoxigenic Escherichia coli c. Salmonella typhi d. Clostridium perfringens 54. Each of the following statements concerning plague is correct EXCEPT Select one: a. Plague is caused by a gram-negative rod. b. Bubonic plague is the most frequent form. c. Plague is transmitted to humans by flea bite. d. Humans are the only natural host of Y. pestis. 55. Which one of the following outcomes is MOST common following a primary herpes simplex virus infec on? Select one: a. Persistent cytopathic effect in infected cells b. Establishment of latent infection c. Complete eradication of virus and virus-infected cells d. Persistent asymptomatic viremia 56. The process in which DNA released by lysis of one bacterium is taken up by a second bacterium, leading to a change in phenotype of that second bacterium, is called ???? Select one: a. transduction b. transfection c. transformation d. conjugation 57. Each of the following statements regarding the techniques for microscopical examina on of bacteria is correct EXCEPT ???? Select one: a. India ink preparation is used for examination of the capsules of organisms. b. Methylene blue is the stain for identifying the bacterial flagella. c. Hanging-drop mount is generally used for studying the motility of bacteria. d. The wet-mount preparation is used mainly for determining motility and gross morphology of the organisms. ti ti  58. Which one of the following is considered a virulence factor for Staphylococcus aureus? Select one: a. Resistance to novobiocin b. Protein A that binds to the Fc portion of IgG c. A heat-labile toxin that inhibits glycine release at the internuncial neuron d. An oxygen-liable hemolysisn 59. Each of the following statements regarding arboviruses is correct EXCEPT Select one: a. The main characteristic that links the various viruses in the arbovirus family is that they are all double-stranded DNA viruses. b. Both yellow fever and dengue are mosquito-borne diseases. c. Travelers to areas where yellow fever is endemic should receive the live, attenuated vaccine. d. Humans and horses are “dead-end” hosts for encephalitis viruses because the concentration of virus in their blood is quite low. 60. Each of the following statements concerning Staphylococci is correct EXCEPT: a.) S. Aureus is differentiated from S. epidermis by the production of coagolase b.) The majority of clinical isolates of S. auerus elaborate penicillinase, therefore presumptive antibiotic therapy for S. Aureus infections should not consist of penicillin G c.) Scalded skin syndrome caused by S. aureus is due to enzymatic degradation of epidermal desmosomes by catalase d.) S. aureus infections are often associated with abscess formation 61. Chemical modi ca on of penicillin G has resulted in several bene cial changes in the clinical use of this drug. Which one of the following is NOT one of the bene cial changes? a.) Lowered frequency of anaphylaxis b.) Increased activity against gram-stain negative rods c.) Increased resistance to stomach acid d.) Reduced cleavage by penicillinase 62. Each of the following statements regarding Rotaviruses is correct EXCEPT a.) Rotaviruses are a leading cause of diarrhea in young children b.) Rotaviruses belong to family Reoviridae, which have double stranded, segmented RNA genome c.) Rotaviruses are transmitted primarily by respiratory droplets fi ti fi fi  d.) A Live attenuated vaccine against rotavirus is available 63. Each of the following statements regarding bacteria agella is correct EXCEPT ???? a.) Flagellins are immunogenic b.) Flagella are composed of a single protein, called flagellin c.) Both rods and cocci have flagella d.) Flagella move bacteria in response to attractant and repellent 64. Each of the following statements concerning the normal ora is correct EXCEPT: a.) The major site where Bacteoides fragilis is found is the colon b.) The most common organism found on the skin is Staphylococcus epidermis c.) Escherichia coli is a prominent member of the normal normal flora of the throat d.) One of the most important sites where Staphylococcus aureus is found is the nose 65. Each of the following statements regarding herpes simplex virus is correct EXCEPT: a.) It is an important cause of neonatal infection b.) Acyclovir can be used to treat primarily lesions in an immunocompetent host c.) Painful vesicular lesions occur on the genitals of both men and women d.) It is an important cause of encephalitis in Adults 66. During the latent period of the virus growth cycle, which one of the following events is LEAST likely to happen ???? a.) Synthesis of capsid proteins b.) Production of Extracellular virions c.) Synthesis of viral RNA d.) Replication of the viral genome 67. Each of the following statements concerning hepa s viruses is correct EXCEPT ???? a.) Because of the presence of serologic tests for hepatitis B and C, the frequency of these hepatitis decline b.) Hepatitis A and Hepatitis E have a fecal- Oral route of transmission c.) In contrast to Hepatitis B, delta hepatitis is not transmitted by blood d.) Delta Agent is a defective virus with an RNA genome and a capsid component of hepatitis B surface antigen 68. All of the following are true EXCEPT that plasmids are extrachromosomal selfreplica ng structures that ???? a.) are vehicles for the dissemination of antibiotic resistance traits among bacteria ti ti ti fl fl  b.) have been found in virtually all medically important bacteria c.) can, in some cases, mediate their own transfer between bacteria d.) are only infrequently transferred by conjugation 69. Each of the following statements regarding varicella- zoster virus is correct EXCEPT ???? a.) In recurrent infections, it causes zoster (shingles), which is characterized by vesicular skin lesions. b.) In primary infections, it causes varicella (chickenpox), which is characterized by vesicular skin lesions c.) Multinucleated giant cells are seen in the lesions d.) It rarely causes disseminated disease in immunocompromised patients. 70. Each of the following statements about Listeria Monocytogenes are true EXCEPT ???? a.) the microbe can only be cultured in human trophoblastic cells b.) neonatal listeriosis occurs as a result of genital tract infection in the gravid female c.) It primarily causes a disease among animals that is occasionally passed in humans d.) meningoencephalitis (meningitis) in the adults is the most commonly recognized form of listeriozis 71. Which one of the following groups of an microbial agents acts on microorganisms by inhibi ng protein synthesis? a.) Fluoroquinolones b.) Aminoglycosides c.) Glycopeptides (eg, vancomycin) d.) Polymyxins e.) Penicillins 72. Each of the following statements regarding Haemophilus in uenzae is correct EXCEPT a.) It is found only in humans; i.e., there is no animal reservoir. b.) Bacteremia is caused by encapsulated strains, but strains without capsules cause disease also. c.) It is a very small, coccobacillary gram-negative rod. ti ti fl d.) Prevention of invasive disease primarily involves personal measures such as hand washing, since there is no vaccine. 73. Each of the following statements regarding chlamydiae is correct EXCEPT a.) Their life cycle consists of a metabolically inactive particle in the extracellular phase. b.) They replicate in the cytoplasm of infected cells, where they form inclusions that are useful diagnostically. c.) They can replicate only within cells because they cannot synthesize sufficient energy for independent growth. d.) They produce an exotoxin that inhibits elongation factor 2. 74. The bacterial structure that mediates adherence of bacteria to mucous membranes is the a.) peptidoglycan b.) Pilus c.) flagellum d.) endotoxin 75. Each of the following statements concerning human immunode ciency virus (HIV) is correct EXCEPT a.) The opportunistic infections seen in AIDS are primarily the result of a loss of cell- mediated immunity. b.) Screening tests for antibodies are useful to prevent transmission of HIV through transfused blood. c.) Zidovudine (azidothymidine) inhibits the RNA-dependent DNA polymerase. d.) The presence of circulating antibodies that neutralize HIV is evidence that an individual is protected against HIV-induced disease. 76. Passive Immuniza on a.) provides protection without hypersensitivity b.) provides immediate protection c.) provides long-lasting protection d.) employs sensitized T cells 77. Each of the following statements concerning the growth of bacteria is correct EXCEPT a.) Some bacteria have a doubling time as short as 30 minutes, whereas others have a doubling time of 10 hours or more. b.) Some bacteria grow in an exponential, logarithmic manner, whereas others undergo meiosis. ti fi  c.) Some bacteria grow in both the presence and the absence of oxygen. d.) Some bacteria use gaseous CO2 as a carbon source, whereas others require carbon in the form of organic molecules. 78. Each of the following statements concerning clostridia is correct EXCEPT a.) Pathogenic clostridia are found both in the soil and in the normal flora of the colon. b.) Antibiotic-associated (pseudomembranous) colitis is due to a toxin produced by Clostridium difficile. c.) Botulism, which is caused by ingesting preformed toxin, can be prevented by boiling food prior to eating. d.) Anaerobic conditions at the wound site are not required to cause tetanus, because spores will form in the presence of oxygen. 79. Which of the following groups are at increased risk for herpes zoster? a.) Patients with atopic dermatitis b.) Pregnant women c.) Infants with genital infections d.) Persons at advanced age e.) Persons who have been vaccinated with varicella vaccine 80. Each of the following statements regarding Candida albicans is correct EXCEPT a.) It causes thrush, a mucosal infection of the oropharynx, which occurs particularly in neonates and immunocompromised patients. b.) Because it does not grow well on laboratory media, the diagnosis of candidal infections is typically made by skin tests that detect a delayed hypersensitivity reaction. c.) The formation of germ tubes is an important diagnostic test. d.) It is a budding yeast when it colonizes the mucous membranes of the mouth. 81. Virus-infected cells o en develop morphologic changes referred to as cytopathic e ects. Which of the following statements about virus-induced cytopathic changes is most accurate? a.) They may include giant cell formation. b.) They are pathognomonic for an infecting virus. c.) They can only be seen with an electron microscope d.) They are rarely associated with cell death. 82. Which one of the following is NOT an important characteris c of either Neisseria gonorrhoeae or Neisseria meningi dis a.) M protein ff ft ti ti  b.) Polysaccharide capsule c.) IgA protease d.) Pili 83. The regula on of enzyme ac vity provides ne control of metabolic pathways. Which of the following regulatory mechanisms provides ne control of a biosynthe c pathway? a.) Feedback inhibition b.) Attenuation c.) Induction d.) None of the above e.) Catabolite repression 84. Each of the following statements about bacteria that grow anaerobically is correct EXCEPT a.) A low oxidation-reduction potential (Eh), such as — 300 mV, is often present where anaerobes grow. b.) Anaerobes are bacteria that require reduced oxygen tension and will not grow on the surface of agar medium in air. c.) Facultative anaerobes can grow only in the presence of less than 10% oxygen. d.) There are both Gram-positive rods and Gram-negative rods that are anaerobes. 85. A 20-year-old Asian woman, a recent immigrant to the United States, develops fever and a cough produc ve of blood-streaked sputum. She has lost 6 kg of body weight in the past 6 weeks. Her chest radiograph shows bilateral upper lobe in ltrates with cavi es. Given the history and chest radiography ndings, which of the following drug regimens would be the best appropriate ini al therapy while awai ng culture results? a.) Ampicillin-sulbactam b.) Cefotaxime, clindamycin, and trimethoprim—sulfamethoxazole c.) Isoniazid, rifampin, pyrazinamide, and ethambutol d.) Vancomycin, gentamicin, and clindamycin e.) Penicillin G and rifampin 86. Each of the following statements regarding Salmonella species is correct EXCEPT fi ti ti ti ti ti ti fi fi ti fi a.) The fecal-oral route is the main mode of transmission. b.) They are non-lactose fermenters and form colorless colonies on EMB agar. c.) They cause diarrhea by producing an exotoxin that activates adenylate cyclase. d.) Their O antigen polysaccharides are an important means of classification. 87. Each of the following statements is correct EXCEPT a.) Influenza viruses have multiple serotypes based on hemagglutinin and neuraminidase proteins located on the envelope surface. b.) Coxsackieviruses are enteroviruses and can replicate in both the respiratory and gastrointestinal tracts. c.) Adenoviruses are RNA enveloped viruses that are an important cause of sexually transmitted disease. d.) Flaviviruses are RNA enveloped viruses that replicate in animals as well as humans. 88. Each of the following statements regarding syphilis is correct EXCEPT ???? a.) In secondary syphilis, both the rapid plasma reagin (RPR) and the fluorescent treponemal antibody-absorbed (FTA-ABS) tests are usually positive. b.) In congenital syphilis, no antibody is formed against Treponema pallidum because the fetus is tolerant to the organism. c.) In tertiary syphilis, lesions commonly appear in the brain and spinal cord, but there are only a few organisms in these lesions. d.) The characteristic lesion of primary syphilis is a painless ulcer. 89. Each of the following statements concerning human immunode ciency virus is correct EXCEPT a.) Patients infected with HIV typically form antibodies against both the envelope glycoproteins (gp120 and gp41) and the internal group-specific antigen (p24). b.) Transmission of HIV occurs primarily by the transfer of blood or semen in adults, but neonates are primarily infected transplacentally. c.) The Western blot test is more specific for HIV infection than the ELISA. d.) HIV probably arose as an endogenous virus of humans since HIV proviral DNA is found in the DNA of certain normal human cells. 90. Each of the following statements concerning pep doglycan is correct EXCEPT a.) It can be degraded by lysozyme. ti fi b.) It is thinner in Gram-positive than in Gram-negative cells. c.) It has backbone composed of alternating units of muramic acid and acetylglucosamine. d.) Cross-links between the tetrapeptides involve D-alanine. 91. Each of the following statements concerning bacterial and human cells is correct EXCEPT a.) Bacterial and human ribosomes are of different sizes and chemical compositions. b.) Bacteria are prokaryotic (i.e., they have one molecule DNA, are haploid, and have no nuclear membrane), whereas human cells are eukaryotic (i.e., they have multiple chromosomes, are diploid, and have a nuclear membrane). c.) Bacterial cells possess peptidoglycan, whereas human cells do not. d.) Bacteria derive their energy by oxidative phosphorylation within mitochondria in a manner similar to human cells. 92. One of the most important procedures in microbiology is the Gram stain. Regarding this stain, which one of the following is LEAST accurate? a.) Exposure of the bacteria to ethanol fixes the crystal violet to the bacterial peptidoglycan. b.) Gram-positive bacteria retain the crystal violet, whereas Gram-negative bacteria do not. c.) Some bacteria, e.g. Mycoplasma lack a cell wall and do not stain with the Gram stain. d.) Gram-positive bacteria appear blue and Gram-negative appear red. 93. Which one of the following viruses is most likely to use upper respiratory tract as its portal of entry? a.) Rota virus b.) Dengue Virus c.) Hepatitis B virus d.) Hepatitis A virus e.) Epstein- Bar Virus 94. Each of the following statements concerning rabies and rabies virus is correct EXCEPT a.) The incubation period is usually long (several weeks) rather than short (several days). b.) The virus has a single antigenic type (serotype). c.) Domestic animals are the most common reservoir. d.) The virus has a lipoprotein envelope and single-stranded RNA as its genome. 95. Each of the following statements regarding the pathogenesis of disease by Neisseria meningi dis is correct EXCEPT ti a.) It usually colonizes the upper respiratory tract and evades secretory IgA by producing a protease specific for that immunoglobulin. b.) Many of the symptoms of meningococcemia can be attributed to endotoxin. c.) It is a gram-negative rod which produces an exotoxin that activates adenylate cyclase. d.) The polysaccharide capsule of this organism is an important virulence factor. 96. Each of the following statements regarding streptococci is correct EXCEPT a.) Group A and group B streptococci are in different groups because they have different polysaccharides in their cell wall. b.) Beta (clear) hemolysis occurs within certain streptococci because they produce enzymes (hemolysins) that lyse red cells. c.) Streptococci are gram-positive cocci that typically form chains. d.) Streptococci are classified primarily by the antigenic differences in their flagella. 97. Regarding viral vaccines, which one of the following is MOST accurate? a.) Killed vaccines are no longer used because they do not induce secretory Ig A. b.) Killed vaccines are safer to give to immunocompromised patients than are live, attenuated vaccines c.) Killed vaccines induce a broader range of immune responses than do live, attenuated vaccines. d.) Killed vaccines induce longer lasting response than do live, attenuated vaccines. 98. The MOST important contribu on of the capsule of Streptococcus pneumoniae to virulence is a.) to retard phagocytosis by polymorphonuclear leukocytes b.) to prevent dehydration of the organisms on mucosal surfaces c.) to inhibit polymorphonuclear leukocyte chemotaxis d.) to accelerate tissue invasion by its collagenaselike activity 99. Each of the following statements concerning hepa s A virus is correct EXCEPT a.) The diagnosis is usually made by isolating the virus in cell culture. b.) The initial site of viral replication is the gastrointestinal tract. c.) Hepatitis A virus commonly causes asymptomatic infection in children. d.) Gamma globulin is used to prevent the disease in exposed persons. ti ti ti  100.Your pa ent has had severe diarrhea for the past 2 days, accompanied by fever and a shaking chill. From both the blood culture and the stool culture, a gram- nega ve rod was isolated that does not ferment lactose. The MOST likely organism is ???? a.) Shigella sonnei b.) Salmonella enteritidis c.) Escherichia coli d.) Haemophilus influenzae 101.Human immunode ciency virus (HIV) is classi ed as a retrovirus. The ra onale for the term “retrovirus” is that ???? a.) the promoter region of the genome RNA is in the reverse position b.) it reverses its morphology from type D to type C, when it enters the cell c.) the genome RNA is transcribed into DNA d.) pieces of the genome RNA are spliced into a single strand before translation 102.Each of the following statements concerning endotoxins is correct EXCEPT a.) They are more stable on heating than exotoxins. b.) They bind to specific cell receptors, whereas exotoxins do not c.) They are less potent (i.e. less active on a weight basis) than exotoxins. d.) They are part of the bacterial cell wall, whereas exotoxins are not 103.Each of the following statements concerning Bacteroides fragilis is correct EXCEPT a.) B. fragilis infections are characterized by foul-smelling pus. b.) B. fragilis is a gram-negative rod that is part of the normal flora of the colon. c.) The capsule of B. fragilis is an important virulence factor. d.) B. fragilis forms endospores, which allow it to survive in the soil. 104.Three organisms, Streptococcus pneumoniae, Neisseria meningi dis, and Haemophilus in uenzae, cause the vast majority of cases of bacterial meningi s. What is the MOST important pathogenic component they share? a.) Endotoxin b.) Protein A c.) Capsule ti ti fl fi fi ti ti ti  d.) β-lactamase 105.Each of the following statements concerning the mechanism of ac on of microbial drugs is correct EXEPT ???? a.) Vancomycin acts by inhibiting peptidoglycan synthesis. b.) Chloramphenicol binds to the 50S ribosomal subunit and inhibits peptidyltransferase. c.) Erythromycin is a bactericidal drug that disrupts cell membranes by a detergentlike action. d.) Aminoglycosides such as streptomycin are bactericidal drugs that inhibit protein synthesis. 106.The ability to use compounds and ions other than oxygen as terminal oxidants in respira on is a widespread microbial trait. This capacity is called: a.) Nitrogen Fixation b.) Substrate phosphorylation c.) Photosynthesis d.) Anaerobic Respiration e.) Fermentation 107.The steps leading to the synthesis of pep doglycan occur in the cytoplasm, on the cytoplasmic membrane, and extracellularly. Which an bio c inhibits an extracellular step in pep doglycan biosynthesis? a.) Bacitracin b.) Rifampin c.) Penicillin d.) Streptomycin e.) Cycloserine 108.Each of the following statements concerning endotoxins is correct EXCEPT a.) Endotoxins are found in most gram-positive bacteria. b.) The toxicity of endotoxins is due to the lipid portion of the molecule. c.) Endotoxins are located in the cell wall. d.) The antigenicity of somatic (QO) antigen is due to repeating oligosaccharides. 109.Interpreta on of hepa s B serologic tests provides important clinical informa on. If your pa ent was HbsAg nega ve, IgM core an body nega ve, and Hbs an body posi ve, which one of the following would be the BEST interpreta on ???? ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti a.) The patient probably has active signs and symptoms of hepatitis. b.) The patient probably has chronic active hepatitis. c.) The patient is probably in the “window” phase. d.) The patient is immune to hepatitis B. 110.Each of the following statements regarding plague is correct EXCEPT a.) The causative organism, Yersinia pestis, is a gram-negative rod with a very low infectious dose. b.) People should not handle dead wild animals since fleas associated with the animals can transmit the disease. c.) The diagnosis must be made serologically because the organism does not grow in culture. d.) There is an animal reservoir for this disease. 111.Which one of the following is NOT an important characteris c of the Lance eld group B streptococci (S. agalac ae)? a.) Vaginal carriage in 5-25% of normal women of childbearing age b.) Pyoderma (impetigo) c.) Beta-hemolysis d.) Neonatal sepsis and meningitis 112.The coagulase test, in which bacteria cause plasma to clot, is used to dis nguish a.) Staphylococcus epidermidis from Neisseria meningitidis. b.) Staphylococcus aureus from Staphylococcus epidermidis. c.) Streptococcus pyogenes from Enterococcus faecalis. d.) Streptococcus pyogenes from Staphylococcus aureus. 113.Each of the following statements concerning cholera toxin is correct EXCEPT a.) Cholera toxin activates the enzyme adenylate cyclase in the mucosal epithelium. b.) Cholera toxin inhibits elongation factor 2 in the mucosal epithelium. c.) Binding of cholera toxin to the mucosal epithelium occurs via interaction of the B subunit of the toxin with ganglioside in the cell membrane. d.) Cholera toxin promotes active secretion of Cl- and HCO3- into the lumen of the gut. 114.Each of the following statements regarding the PPD (tuberculin) skin test is correct EXCEPT ???? ti ti ti fi a.) A positive test indicates that the person has formed a delayed-hypersensitivity response against certain proteins of Mycobacterium tuberculosis. b.) A positive test indicates that the person should receive isoniazid (INH) and rifampin for 9 months. c.) A positive test is judged by the amount of induration, i.e., thickening, of the skin at the site of injection. d.) A positive test indicates that the person has been infected with M. tuberculosis but may not have symptoms of disease at present. 115.Regarding the e ect of benzylpenicillin (penicillin G) on bacteria, which one of the following organisms is LEAST likely to be resistant? a.) Staphylococcus aureus b.) Neisseria gonorrhoeae c.) Streptococcus pyogenes d.) Enterococcus faecalis 116.Which one of the following is NOT a component of pep doglycan? a.) Lipid A b.) Pentaglycine c.) Diaminopimelic Acid d.) N- Acetyl muramine acid e.) N- Acetyl glucosamine 117.Each of the following statements regarding hepa s A and Hepa s B viruses is correct EXCEPT ???? a.) Hepatitis B surface antigen (HbsAg) is the component in the Hepatitis B vaccine that induces protective antibody b.) The presence of hepatitis E antigen (HbsAg) in certain patient’s blood indicated that the blood is likely to be infectious c.) In certain patients, hepatitis B virus causes persistent infections and infectious virus is present in the blood d.) Certain patients have antibody to hepatitis A virus in their blood, indicating that a chronic carrier state is present 118.Each of the following statements regarding Bacterial Cytoplasmic membrane is correct EXCEPT ???? a.) Bacterial cytoplasmic membrane consists of inner phospholipid layer and outer lipopolysaccharide layer b.) It is a functional analogue of the mitochondrial membrane ff ti ti ti ti ti c.) It is the site of the specific enzyme (permeases) which facilitates the transport of molecules into the Cell d.) The invagination of cytoplasmic membrane, called mesosome, participates in cell division 119.Each of the following statements regarding Streptococcus pyogenes is correct EXCEPT a.) Since it is commonly found as part of the normal flora of the colon, transmission typically involves fecal- oral spread. b.) Pathogenesis of acute glomerulonephritis involves antibodies formed against antigens of certain strains of S. Pyogenes c.) It is the most common cause of bacterial pharyngitis d.) Patients can have multiple episodes of S. Pyogenes infections since there are multiple allergic types of M Protein 120.Each of the following agents is a recognized cause of diarrhea EXCEPT a.) Vibrio cholera b.) Clostridium perfringens c.) Enterococcus faecialis d.) Yersinia Enterocollitica 121.In which one of the following infec ons to anaerobic bacteria NOT have an important role? a.) Abdominal Abscess b.) Impetigo (pyoderma) c.) Pseudomembranous colitis d.) Gas gangrene 122.Which one of the following statements concerning the organisms that cause brucellosis is CORRECT? a.) Brucellae are found in reciculoendothelial cells and often cause granulomatous lesions b.) The principle reservoirs of Brucellae are small rodents c.) Brucellae are obligate intracellular parasites that are usually identified by growth in human cell culture d.) Brucellae are transmitted primarily by tick bite 123.Each of the following statements regarding Mycobacterium tuberculosis is correct EXCEPT ???? ti  a.) It is transmitted by aerosols droplets b.) In cavity disease, the sputum contains rods that stain red with the acid- fast stain. c.) The predominant cells found in cavitary lesions are neutrophils d.) Multidrug therapy is required for months to treat cavitary diseases 124.Each of the following statements regarding T Cells is correct EXCEPT ???? a.) Developing T Cells typically express both CD4 and CD8 proteins, but mature T Cells express only one or the other b.) In the thymic education of T Cells, clones of cells that react with self-MHC and foreign antigen are deleted c.) T Cells originate in the marrow bone must pass through the thymus to differentiate properly d.) T Cells plat an essential role in delayed hypersensitivity reactions e.g. the tuberculin skin test 125.Amino Acids are found in the protein, pep doglycan, and capsule of bacteria. Which of the following amino acids is found only in pep doglycan? a.) L- Lysine b.) None of the above c.) L- Alanine d.) Diaminopimelic Acid e.) D- Glutamate 126.Which one of the following viruses possesses an RNA genome that is infec ous when puri ed? a.) Measles virus b.) Influenza Virus c.) Poliovirus d.) Rotavirus e.) Papilomavirus 127.Each of the following statements about both measles and rubella virus is correct EXCEPT a.) Their virons contain an RNA Polymerase b.) They are RNA enveloped viruses c.) They are transmitted by respiratory aerosols d.) They have a single antigenic type fi ti ti ti  128.The shingles vaccine is recommended for which of the following groups a.) Individuals older than age 60 years b.) Healthy adolescents c.) Those who never had chickenpox d.) Pregnant woman 129.Each of the following statement concerning the killing of bacteria is correct EXCEPT a.) Silver Nitrate can inactivate bacterial enzymes b.) Ultraviolet light can degrade bacterial capsules c.) Lysozomes in tears can hydrolyze bacterial cell walls d.) Detergents can disrupt bacterial cell membrane 130.Each of the following statements concerning gram- nega ve rods is correct EXCEPT a.) Invasive disease caused by Haemophilus is most often due to strains possessing a type b polysaccharide capsule b.) Legionella pneumophila infection is acquired by inhalation of aerozols from environmental water sources c.) Whooping cough, which is caused by Bordetella pertussis is on the rise because changing antigenicity has made the vaccine relatively infective d.) Pseudomonas aeruginosa causes wound infections that are characterized by blue- green pus as a result of pyocyanin production 131.Regarding HBV and the disease hepa s B, which one of the following is most accurate? a.) A person in the “window period” can be diagnosed as having been infected by HBV if antibody to the HBsAg is present b.) HBV has a circular, partially double- stranded DNA as its genome and has DNA Polymerase in the virion ti ti ti  c.) Health care personal who sustain needle stick injury while taking blood from a person with hepatitis B should receive acyclovir d.) HBV infection induces antibody to HBcAg (core antigen), which protects the person from a second attack by the same strain of HBV e.) The most reliable indicator that the person can transmit HBV is the presence of HBsAg in the blood 132.The biosynthe c origin of building blocks and coenzyme can be traced back to rela vely few precursors called focal metabolites. Which of the following are focal metabolites? a.) a- Ketoglutarate b.) All of the above c.) Oxaloacetate d.) Phosphoenolpyruvate e.) Glucose 6- Phosphate 133.Each of the following events involves gene c recombina on EXCEPT a.) Transposition of a mobile genetic element b.) Integration of a temperate bacteriophage c.) Conjugation, e.g. transfer of an R (resistance) factor d.) transduction of a chromosomal gene 134.Complement xa on refers to ???? a.) the destruction of complement in the serum by heating at 56o C for 30 minutes b.) the ingestion of C3b- coated bacteria by macrophages c.) the interaction of C3b with mast cells d.) the binding of complement components by antigen- antibody complexes ? 135.Which of the following statements concerning Legionella pneumophila is CORRECT? a.) It is an important cause of pneumonia in renal transplant patients b.) It is part of the normal flora of the colon c.) It does not have a cell wall d.) It cannot be grown on Laboratory media 136.A 19- years-old female college student has a fever, sore throat, and lymphadenopathy associated by lymphocytosis with atypical cells and an increase in sheep cell agglu nins. The diagnosis is most likely: a.) Viral meningitis b.) Chickenpox ti fi ti ti ti ti ti  c.) Herpes Simplex Virus d.) Infectious mononucleosis e.) Infectious hepatitis 137.Each of he following statements regarding toxin-mediated diseases is correct EXCEPT a.) Botulism is characterized by muscle weakness and is caused by a toxin that inhibits the release of acetylcholine b.) Pseudomembranous colitis is a toxin mediated disease caused by Clostridium difficile c.) Tetanus toxin is a neurotoxin that acts at the level of the synapses in the central nervous system d.) Trachoma is a toxin- mediated disease caused by Coxiella bumetii 138.The iden ca on of bacteria by serologic test is based on the presence of speci c an gens. Which one of the following compounds of the cell is LEAST likely to contain useful an gens? a) Ribosomes b.) Cell wall c.) Flagella d.) Capsule 140.Each of the following statements regarding Bacteroides fragilis is correct EXCEPT a.) It is a gram- positive, spore forming rod b.) Tissue infected by this organism typically contains foul- smelling pus and gas c.) It is typically found in mixed infections, e.g., with facultative bacteria such as E. Coli d.) Its natural habitat is the human colon 141.Each of the following statements concerning gram- nega ve rods is correct EXCEPT ???? a.) Klebsiella pneumoniae, although a cause of pneumonia, is a part of the normal flora in the colon b.) E. Coli ferments lactose, whereas the enteric pathogens Shigella and Salmonella do not c.) Escherichia coli is part of the normal flora in the colon; therefore, it does not cause diarrhea d.) Proteus species are highly motile organisms that are found in the human colon and cause urinary tract infections 142.Each of the following statements regarding in uenza is correct EXCEPT ???? ti ti fi ti ti fl ti fi a.) Influenza A virus undergoes major antigenic changes in its hemagglutinin (antigenic shift), which allows the virus to evade existing immunity b.) Influenza viruses cannot be grown in cell culture; hence, the diagnosis can only be made serologically c.) Influenza A virus causes more epidemics and more serious disease than influenza B and C viruses do d.) Influenza viruses are transmitted primarily by aerosol and primarily affect the lower respiratory tract 143.Each of the following statements regarding Pseudomonas Aeruginosa is correct EXCEPT a.) It is an important cause of wound and burn infections b.) It is commonly resistant to many antibiotics c.) It produces neither exotoxins nor endotoxin d.) It is commonly associated with water sources 144.Each of the following statements regarding bacterial metabolism is correct EXCEPT a.) Glyceraldehyde-3- phosphate and pyruvate are required for further assimilatory or dissimilatory reactions within the cell b.) The major source of phosphate for phosphorylation of glucose or other hexoses is ATP, not inorganic phosphate (Pi) c.) Like eukaryotes, in bacteria glucose oxidation may occur only only by pathway d.) NADH + H+ or NADPH + H+ is generated as reducing equivalents directly by enzymatic reactions involved in metabolic pathways 145.Each of the following statements regarding Corynebacterium diphtheriae and the disease diphtheria is correct EXCEPT a.) A Gram stain of the exudate from a lesion reveals gram- positive rods b.) Diphtheria toxin blocks proteins synthesis in human ells by inhibiting elongation factor 2 c.) The antigen in the vaccine is diphtheria toxoid d.) The natural habitat of the organism is the soil, where it forms spores. Inhabitation of spores is the main mode of transmission 146.Each of the following statements concerning the normal ora is correct EXCEPT a.) The normal flora of the colon consists predominantly of anaerobic bacteria b.) The presence of the normal flora prevents certain pathogens from colonizing the upper respiratory tract c.) Organisms of the normal flora are permanent residents of the body surfaces d.) Fungi, e.g., yeasts, are not members of the normal flora 147.Regarding the preven on of bacterial diseases by vaccines, which one of the following is LEAST accurate ???? ti fl  a.) Both the pertussis vaccine and the Haemophillus influenza vaccine contain inactivated whole bacteria ad produce significant side effects in children b.) The tetanus vaccine contains tetanus toxoid. The toxoid is produced by treating tetanus toxin with formalin, which inactivates its ability to cause disease but leaves its antigenicity intact c.) The pneumococcal vaccine contains the capsular polysaccharide of many serotypes and is recommended primarily for older people d.) Both the tetanus and diphtheria vaccine should be given in childhood. These vaccines are 148.The endotoxin of gram- nega ve bacteria is associated with a.) mesosome b.) cytoplasmic membrane c.) capsule d.) cell wall 149.Each of the following statements regarding Mycobacterium leprae is correct EXCEPT a.) Cell- mediated immunity is the most important host defense b.) Diagnosis involves culturing the organism on bacteriologic medium c.) Many patients have sensory nerve destruction and lose sensation d.) Humans constitute the major reservoir 150.Each of the following statements concerning C. Albicans is correct EXCEPT a.) C. Albicans is transmitted primarily by respiratory aerosol b.) C. Albicans causes thrush c.) Impaired cell- mediated immunity is an important predisposing factor to disease d.) C. Albicans is a budding yeast that forms pseudohyphae when it invades tissue 151.The forma on of a ma ng pair during the process of conjuga on in E. Coli requires a.) A sex pilus b.) Integration of a transposon c.) Lysis of the donor d.) Transfer of both strands of DNA e.) a restriction endonuclease ti ti ti ti  152. All of the following compounds are found in the cell walls of certain bacteria EXEPT a.) Peptidoglycan b.) Chitin c.) Diaminopimelic acid d.) Teichoic acid 153. Each of the following statements concerning Corynebacterium diphtheriae is correct EXCEPT a.) Antitoxin should be used to treat patients with diphtheria b.) Diphtheria is toxoid should not be given to children under the age of 3 years because the incidence of complications is too high c.) C. diphtheriae is a non- spore forming gram – positive rod d.) Toxin production is dependent on the organism’s being lysogenized by a bacteriophage 154. Of the organisms listed below, which one is the MOST frequent bacterial cause of pharyngi s? a.) Neisseria meningitides b.) Streptococcus pneumoniae c.) Streptococcus pyogenes d.) Staphylococcus aureus 155.A culture of skin lesions from a pa ent with pyodermia (impe go) shows numerous colonies surrounded by a zone of the beta hemolysis on a blood agar plate. A Gram – stained smear shows a gram – posi ve cocci. If you found the catalase test to be nega ve, which one of the following organisms would you MOST probably have isolated? a.) Staphylococcus aureus b.) Streptococcus pneumoniae c.) Streptococcus pyogenes d.) Neither S. Pyogenes nor S. aureus 156.Some viruses encode for a Viral RNA- dependent RNA polymerase. Which of the following states a principle about viral RNA polymerase? ti ti ti ti ti  a.) Negative- strand RNA viruses supply their own RNA- dependent RNA polymerase because eukaryotic cells lack such enzymes b.) All RNA Viruses carry RNA Polymerase molecules inside virus particles because they are needed to initiate the infectious cycle c.) The viral RNA polymerase protein also serves as a major core structural protein in the virus particle d.) Antibodies against the viral RNA Polymerase neutralize virus infectivity 157.Which one of the following is the most reasonable explana on for the ability of Hepa s B virus to cause chronic infec on? a.) Many humans are immunologically tolerant to HbsAG b.) Infection does not elicit the production of antibody c.) Viral DNA may become integrated into the chromosomal DNA of he host cell d.) The liver is an immunologically sheltered site 158.Lysosime degrades a.) RNA Polymerase b.) Peptidoglycan c.) Capsular polysaccharide d.) Lipid A 159.Regarding measles virus and the disease measles, which one of the following statement is most accurate? a.) The measles vaccine contain killed virus as the Immunogen b.) Fecal- oral transmission during the diaper stage is the main mode of acquisition of measles virus c.) One of the main sequelae of measles is autoimmune glomerulonephritis and kidney failure d.) Measles is unlikely to be eradicated because there is a significant animal reservoir for this virus e.) This virus has only one antigen type, and lifelong immunity occurs in patients who have had measles. 160.Each of the following statements regarding the Gram stain technique is correct EXCEPT a.) Inflammatory cells appear Gram- negative, where as fungi appear Gram- Positive ti ti ti ti  b.) Organisms that retain the crystal- violet iodine complex are dark blue and are called Gram- Positive c.) The basis of this reaction is the structure of the cell membrane. d.) Organisms that lose the primary complex and take up the secondary dye safranin appear red and are called gram negative 161.The an body- binding site is formed primarily by a.) the variable regions of H Chains b.) The constant regions of H and L Chains c.) The variable regions of L Chains d.) The hypervariable regions of H and L Chains 162.The most common congenital infec on is caused by: a.) Parvovirus b.) Herpes simplex virus type2 c.) Human herpes virus 8 d.) Cytomegalovirus e.) Varicella- zoster Virus 163.Viruses belonging to which of the following groups are likely to establish latent infec ons? a.) Herpesvirus b.) Filovirus c.) Influenza Viruses d.) Caliciviruses e.) Poxviruses 164.Each of the following statements concerning Staphylococcus aureus is correct EXCEPT a.) The coagulase test is positive b.) Endotoxin is an important pathogenic factor c.) Gram- positive cocci in grapelike cluster are seen on Gram- stained smear d.) Treatment should include a β-lactamase resistant penicillin 165.Regarding Hepa s C Virus (HCV) which one of the following is most accurate? ti ti ti ti ti  a.) The cilled vaccine against HCV is poorly immunogenic, so booster doses must be given at least every 5 years b.) HCV is a defective virus that requires concurrent HBV infection in order to replicated c.) Chronic infection with HCV occurs less frequently than chronic infection with HBV d.) Chronic infection with HCV predisposes to hepatocellular carcinoma 166.Complete killing of all living organisms from a par cular loca on or material is accomplished by a) boiling b.) disinfection c.) pasteurization d.) Sterilization 167.Each of the following statements concerning wound infec ons caused by Clostridium per ngens is correct EXCEPT a.) Anaerobic culture of the wound site should be ordered b.) An exotoxin plays a role in pathogenesis c.) Gram- positive rods are found in the exudate d.) The organism grows only in human cell culture 168.Each of the following statements about human immunode ciency virus (HIV) is correct EXCEPT a.) The virion contains an RNA- dependent DNA Polymerase b.) HIV is an enveloped RNA Virus c.) A DNA copy of the HIV genome integrates into host cell DNA d.) Acyclovir inhibits HIV replication 169.What type of Hepa s B Vaccine is currently in Use? a.) Synthetic peptide vaccine b.) Killed- virus vaccine c.) Subunit vaccine produced using recombinant DNA d.) Attenuated live- virus vaccine 170.Your pa ent is a drug addict who has the symptoms of sep cemia. You do a blood culture, which reveals Staphylococcus aureus. Unfortunately, the laboratory reports that the organism is penicillin- resistant. Which one of the following is the LEAST accurate ???? ti fi ti ti ti ti fi ti ti a.) The organism may produce β-lactamase b.) The organism may have altered penicillin- binding proteins c.) Resistance may be due to the production of catalase by the organism d.) Resistance may be due to inability of the penicillin to penetrate inside the Organism 171.Regarding the func ons of an bodies, which one of the following is LEAST accurate ????? a.) Because the gamma heavy chain of IgG bindings complement, IgG is frequently involved in diseases caused by immune complexes b.) Because IgA is the main immunoglobulin found in respiratory tract secretions, it is frequently involved in anaphylactic hypersensitivity c.) Because IgM is made early in the primary response, it is a good indicator of current infection d.) Because IgG crosses the placenta, it Is the main immunoglobulin in fetal blood 172.Cytotoxic T cells are involved in all of the following func ons EXCEPT ???? a.) tumor destruction b.) Lysis of cells infected with viruses c.) Antigen presentation d.) Autoimmune diseases 173.Regarding herpes simplex virus type 1 and varicella- zoster virus which, one of the following is LEAST accurate ???? a.) They both cause disseminated disease in patients with reduced cell- mediated immunity b.) They both have a reservoir in domestic animals that serve as a source of virus infection for humans c.) They both cause vesicular skin lesions d.) They both cause multinucleated giant cells to form in the skin lesions 174.The synthesis of which of the following cell components is dependent on a Template? a.) Peptidoglycan b.) Lipopolysaccharide c.) Phospholipids d.) Capsular Polysaccharide e.) Deoxyribonucleic acid ti ti ti  175.A Posi ve tuberculin skin test (a delayed hypersensi vity reac on) indicates that a.) Only the B Cell systems is functional b.) A Cell- mediated immune response has occurred c.) A humoral immune response has occurred d.) both the T and B cell systems are functional 176.Each of the following statements concerning bacterial spores is correct EXCEPT a.) Spores are resistant to boiling b.) Spores are metabolically inactive and contain dipicolinic acid, a calcium blocker c.) Spores are formed under adverse environmental Conditions such as the absence of Carbon source d.) Spores are formed primarily by organisms of the genus Neisseria 177. Which of the following statements concerning mumps is CORRECT? a.) since there is no vaccine against mumps, passive immunization is the only means of preventing the disease. b.) second episodes of mumps can occur since there are 2 serotypes of the virus and protection is type-specific. c.) the diagnosis of mumps is made on clinical grounds since the virus cannot be grown in cell culture and serologic tests are inaccurate. d.) although the salivary glands are the most obvious sites of infection, the testes, ovaries, and pancreas can be involved as well. 178. Microorganisms that can grow best at low O2 concentration and can also grow without O2 are called: a.) strict anaerobes b.) microaerophilic ? c.) facultative anaerobe d.) aerobes 179. Each of the following statements concerning arboviruses is correct EXCEPT a.) there is a live, attenuated vaccine that effectively prevents yellow fever. b.) the pathogenesis of dengue hemorrhagic shock syndrome is associated with the heterotypic anamnestic respiration. c.) wild birds are the reservoir for encephalitis viruses but not for yellow fever viruses ti ti ti d.) ticks are the main mode of transmission for both encephalitis and yellow fever 180. Regarding the movement of genes within a bacterium or from one bacterium to another, which of the following is the LEAST accurate? a.) bacteria can acquire new genes when they are infected by viruses, a process called transduction b.) transposons can move antibiotic resistance genes from the bacterial chromosome to a plasmid. c.) resistance plasmids (R factors) can be transferred from one bacterium to another by conjugation d.) lysogeny is the process by which genes are exchanged between one site on the bacterial chromosome and another site on the bacterial chromosome. 181. Each of the following statements about human immunodeficiency virus (HIV) is correct except a.) HIV is an enveloped RNA virus b.) A DNA copy of HIV genome integrates into host cell DNA c.) the vision contains an RNA- dependent DNA polymerase d.) Acyclovir inhibits HIV replication. 182. A woman who is HBsAg positive and HBsAb negative has given birth. Which of the following is the most appropriate thing to do for the newborn? a.) immunize with vaccine containing HBsAg (HBV vaccine) b.) gave hepatitis B hyperimmune globulins (HBIG) c.) give both the HBV and HBIG d.) nothing. The child is protected against hepatitis B. 183. Complete killing of all living organisms from a particular location or material is accomplished by a.) pasteurization b.) sterilization c.) boiling d.) disinfection 184. A secondary immune response is more rapid and intense than a primary immune response, the MOST likely explanation of this observation is that a.) a pool of memory B cells is generated during the primary response b.) antigen presentation is more rapid in the secondary response c.) antigen persists longer in the secondary response d.) a pool of both memory B cells and memory T cells is generated during the primary response 185. Which of the following groups of antimicrobial agents acts on microorganisms by inhibiting protein synthesis? a.) polymyxins b.) fluoroquinolones c.) penicillins d.) aminoglycosides e.) glycopeptides (e.g vancomycin) 186. Regarding various gram-negative rods, which one of the following is the LEAST accurate? a.) the O antigens of E.coli and Klebsiella are enterotoxins that cause diarrhea b.) gram-negative rods have endotoxin in their wall. Endotoxin is a lipopolysaccharide whose toxic component is lipid A. c.) E.coli is part of the normal flora of the colon. It can be distinguished From salmonella and shigella, which are 2 important enteric pathogens, by lactose fermentation. i.e , E. Coli ferments lactose whereas the others do not. d.) Klebsiella, Enterobacter, and Serratia are part of the normal flora of the colon, they are the cause of nosocomial (hospital) outbreaks of pneumonia and urinary tract infections. 187. Which one of the following statements is the MOST accurate comparison of human, bacterial, and fungal cells? a.) Human and fungal cells have a similar cell wall, in contrast to bacteria, whose cell wall contains peptidoglycan. b.) Human and fungal cells have similar ribosomes, whereas bacterial ribosomes are different. c.) Human cells undergo mitosis, whereas neither bacteria nor fungi do. d.) Human and bacterial cells have plasmids, whereas fungal cells do not. 188. Each of the following statements regarding prions is correct EXCEPT: a.) Prions are small protein particles b.) They cause plant diseases c.) They can replicate only within host cells d.) They do not have nucleic acids 189. Biologic activities associated with the Fc fragment of an IgG molecule include all of the following EXCEPT: a.) binding to phagocytes b.) placental transport c.) antigen binding d.) complement binding 190. The classic complement pathway is initiated by interaction of C1 with a.) factor B b.) bacterial lipopolysaccharides c.) antigen-IgG complexes d.) antigen 191. Each of the following statements concerning penicillin is correct EXCEPT a.) the B-lactam ring of penicillin is required for its activity b.) the structure of penicillin resembles that of a dipeptide of alanine, which is a component of peptidoglycan c.) Penicillin is a bacteriostatic drug since autolytic enzymes are not activated d.) Penicillin inhibits transpeptidases, which are required for cross-linking peptidoglycan. 192. Which of the following phrases accurately describes viral neutralising antibodies? a.) induced by disease causing viruses b.) directed against viral nucleic acid sequences c.) of little importance to immunity to viral infection d.) appear in the host sooner after viral infection than interferon e.) directed against viral protein on the outside of the virus particle. 193. Each of the following statements regarding Streptococcus pneumoniae is correct EXCEPT a.) There are at least 80 serotypes of pneumococci, which are distinguished on the basis of their capsular polysaccharides. b.) pneumococci are gram-positive diplococci that form alpha-haemolytic (green) colonies on blood agar. c.) pneumococci are distinguished from viridans streptococci by their appearance on blood agar plate. 194. Your patient is a woman who is due to give birth next week. She asks you about the risk of her baby becoming infected with herpes simplex virus type 2. Which of the following is the most accurate response? a.) the risk is higher if the woman has IgG antibody to HSV-2 than if she has IgM antibody. b.) the risk is higher if the mother is having an episode of recurrent disease caused by HSV-2 than if it were a primary episode c.) the risk is higher if the delivery occurs by cesarean section than if the delivery is performed vaginally. d.) the risk is higher if the mother has visible lesions than if she does not e.) HSV-2 is a significant cause of congenital abnormalities. 195. Each of the following statements regarding antiviral drugs is correct EXCEPT a.) Amantadine prevents influenza A virus from replicating by inhibiting uncoating of the virus into the infected cell. b.) Azidothymidine (AZT) prevents human immunodeficiency virus from replicating by inhibiting the binding of the virus to the cell surface receptor ? c.) Acyclovir prevents herpes simplex virus type 1 from replicating by inhibiting the DNA polymerase of the virus. d.) Gancyclovir prevents the replication of cytomegalovirus 196. Each of the following statements regarding bacterial flagella is correct EXCEPT a.) Flagellins are immunogenic b.) Both rods and cocci have flagella c.) Flagella are composed of a single protein called flagellin d.) Flagella move bacteria in response to attractant and repellant 197. The synthesis of which of the following cell components is determined entirely by enzyme specificities? a.) Lipopolysaccharide b.) DNA c.) Protein d.) Flagella e.) Ribosomal RNA 198. Regarding the Varicella-zoster virus (VZV), which of the following is MOST accurate? a.) the vaccine against varicella contains all three serotypes of formalin-killed VZV as the immunogen. b.) High-dose acyclovir can eliminate the latent state caused by VZV c.) the principal site of latency of VZV is in the nucleus of motor neurons d.) domestic animals such as pigs and chickens are the main reservoir for VZV e.) when Zoster occurs in an immunocompromised patient, acyclovir should be given to prevent disseminated infection. 199. The primary route of carbon assimilation used by organisms that use CO, as a sole source of carbon is ?? Should be CO2?? a.) hexose monophosphate shunt b.) glyoxalate cycle c.) Embden-Meyerhof pathway d.) Calvin cycle e.) Enter-Doudoroff pathway 200. Each of the following statements concerning viral serotypes is correct EXCEPT a.) some viruses have multiple serotypes b.) some viruses have an RNA polymerase that determines the serotype c.) in enveloped viruses, the serotype is usually determined by the outer envelope proteins, especially the spike proteins d.) in naked nucleocapsid viruses, the serotype is usually determined by the outer capsid proteins 201. Each of the following statements concerning Neisseria Meningitidis is correct EXCEPT a.) it contains endotoxins in its cell wall b.) it is an oxidase-positive, gram negative diplococcus c.) it produces an exotoxin that stimulates adenyl cyclase d.) it has a polysaccharide capsule that is antiphagocytic 202.Comparing anaphylactic and immune complex hypersensitivities, which one of the following is MOST accurate? a.) After contact with antigen, symptoms appear more rapidly in immune complex reactions than in anaphylactic reactions b.) Less antigen is required for a reaction in immune complex hypersensitivity than in anaphylactic hypersensitivity c.) IgE participates to a greater extent in immune complex hypersensitivity than in anaphylactic hypersensitivity d.) Complement participates in immune complex hypersensitivity but not in anaphylactic hypersensitivity 203. Each of the following statements regarding the mode of action of antimicrobial drugs is correct EXCEPT ???? a.) Quinolones, e.g., norfloxacin inhibit bacterial DNA synthesis by inhibiting the gyrase that unwinds DNA b.) Both aminoglycosides and tetracyclines act by inhibiting protein synthesis c.) Amphotericin B inhibits certain fungi but is ineffective against most bacteria because it binds much more efficiently to fungal ribosomal proteins than to those in bacteria d.) The reason why sulfonamides selectively inhibit the growth of bacteria more than human cells is that bacteria must synthesize folic acids, whereas human cells do not 204. Certain viruses possess an outer structure called an envelope. Regarding the viral envelope, which one of the following is LEAST accurate ???? a.) Enveloped viruses are more easily inactivated by lipid solvents than are nonenveloped viruses b.) Proteins in the envelope interact with neutralizing antibody c.) Proteins in the envelope determine host cell specificity d.) When RNA polymerases are present in a virus, they are typically found as one of the envelope proteins 205. S. Pneumoniae resistance to penicillin is caused most often by ???? a.) The action of acetyltransferase b.) The action of ß-lactamase c.) Substitution of the d-Ala-d- Ala dipeptide with d-Alad-Lac-dipeptide in the cell wall peptidoglycan d.) Genetically modified binding proteins in the bacterial cell wall e.) Decreased permeability of the bacterial cell wall 206. Each of the following statements concerning the mechanisms of resistance to antimicrobial drugs is correct EXCEPT a.) Resistance to some drugs is due to transposon genes that code for enzymes, which inactivate the drugs b.) Resistance to some drugs is due to a chromosomal mutation that alters the receptor for the drug c.) R Factors are plasmids that carry the genes for enzymes, which modify one or more drugs d.) Resistance genes are rarely transferred by conjugation 207. Each of the following statements regarding bacterial spores is correct EXCEPT a.) They are formed primarily by gram- negative cocci such as Neisseria b.) They are formed primarily when the organism has inadequate nutrients c.) Most bacterial spores can survive in the soil for long periods (years) d.) They require temperatures above boiling in order to be killed 208. Bacteria commonly reproduce by: a.) Binary fusion b.) Spore formation c.) Elaborate mitotic division d.) Bug formation 209. Which one of the following statements BEST explains the relationship between inflammation of the heart (carditis) and infection with group A beta- hemolytic streptococci? a.) Streptococci contain an antigen which triggers production of antibodies cross- reactive with heart tissue. b.) Streptococci are polyclonal activators of B Cells c.) Streptococci are polyclonal activators of T Cells d.) Immune complexes of Streptococcal antigen and antibody are deposited in heart tissue 210. Select the one lettered answer that is best. Prokaryotic Cells a.) generate adenosine triphosphate (ATP) in the mitochondria b.) Contain 80S ribosomes c.) Are all motile d.) lack nuclear membrane 211. Each of the following statements concerning the mechanism of action of antibacterial drugs is correct EXCEPT a.) Penicillins are bactericidal drugs that inhibit the transpeptidase reaction and activate autolytic enzymes b.) Aminoglycosides are bacteriostatic drugs that inhibit protein synthesis by activating ribonuclease, which degrades mRNA c.) Erythromycin is a bacteriostatic drug that inhibits protein synthesis by blocking d.) Tetracyclines are bacteriostatic drug that inhibits protein synthesis by blocking tRNA binding 212. Each of the following statements regarding hepatitis A virus is correct EXCEPT a.) There is no vaccine to prevent the disease b.) Immunity after injection is typically lifelong c.) It is transmitted by the fecal- oral route d.) Most childhood is mild or inapparent 213. The phospoenol-phosphotransferase system (PTS) a.) does not require the heat-stable protein b.) phosphorylates the transported substances c.) is used to transport fatty acids d.) is basically an example of a facilitated diffusion 214. Aminoglycoside antibiotics usually cause which of the following adverse events? a.) they cause photosensitivity b.) they cause aplastic anaemia c.) they cause nonspecific stimulation of B cells d.) they cause ototoxicity and nephrotoxicity 215. Bacteria differ from viruses in several structural and chemical characteristics. Which one of the following is LEAST accurate? a.) Bacteria have ribosomes, whereas viruses do not b.) most bacteria have mitochondria, whereas viruses do not. c.) bacteria are cells, whereas viruses are not d.) most bacteria contain peptidoglycan, whereas viruses do not. 216. Each of the statements about the classification of streptococci is correct EXCEPT a.) Although pneumococci and the viridian’s streptococci are alpha-haemolytic, they can be differentiated by the bile solubility test and their susceptibility to optochin. b.) viridans streptococci are identified by lancefield grouping, which is based on the C carbohydrate in the cell wall c.) Pneumocicci (streptococcus pneumoniae) are alpha-haemolytic and can be serotyped on the basis of their polysaccharide capsules. d.) enterococci can be identified by their ability to grow in 6.5% sodium chloride. 217. Each of the following statements concerning resistance to antibiotics is correct EXCEPT a.) resistance to aminoglycosides can be due to phosphorylating enzymes encoded by R plasmids b.) Resistance to penicillin can be due to alterations in binding proteins in the cell membrane c.) resistance to tetracycline is primarily due to failure to achieve adequate concentrations of drug within the bacteria d.) resistance to sulfoamides is primarily due to enzymes that hydrolyze the 5-membered ring structure 218. Five days ago a 65-year woman with lower urinary tract infection began taking ciprofloxacin. She now has fever and severe diarrhea. Of the organisms listed, which one is MOST likely to be the cause of the diarrhea? a.) Clostridium defficile b.) Bordetella petrussis c.) Bacteroides fragilis d.) Proteus mirabilis 219. Each of the following statements concerning the structure and chemical composition of bacteria is correct EXCEPT a.) some gram-positive cocci contain a layer of teichoic acid external to the peptidoglycan b.) some gram-positive rods contain dipicolinic acid in their spores c.) some mycoplasmas contain pentaglycine in their peptidoglycan. d.) Lipid A is a part of the lipopolysaccharide in the cell wall of the gram negative bacteria responsible for the endotoxic shock 220. Each of the following statements concerning exotoxins is correct expect a.) Some exotoxins act in the gastrointestinal track to cause diarrhea. b.) Some exotoxins contain lipopolysaccharides as the toxic component. c.) When treated chemically, some exotoxins lose their toxicity and can be used as Immunogen in vaccines. d.) Some exotoxins are capable of causing disease in purified form, free of any bacteria. 221, All of the following statements about Plasmids are true EXEPT that plasmids a.) carrying resistance genes for antibiotics for antibiotics are called R plasmids b.) Are vehicles for the dissemination of antibiotic- resistant traits among bacteria c.) Are conjugate when they contain sufficient genetic information to enable them to mediate their own transfer by conjugation d.) Never control genes regulating enzymes capable of destroying antimicrobial drugs 223, Each of the following statement concerning the killing of bacteria is correct EXCEPT a.) An autoclave uses steam under pressure to reach the killing temperature of 121o C b.) A 70% solution of ethanol kills effectively vegetative bacteria c.) The pasteurization of milk kills pathogens pathogens but allows many organisms and spores to survive d.) Iodine kills by causing the formation of thymine dimers in bacteria DNA 224, Each of the following statements regarding the selective action of antibiotics on bacteria is correct EXEPT a.) Penicillin affects bacteria rather than human cells since bacteria have a peptidoglycan human cells do not b.) Both sulfonamides and trimethoprim affect folic acid synthesis in bacteria, a pathway that does not occur human cells c.) Isoniazid effects the DNA polymerase of bacteria but not that of human cells d.) Chloramphenicol affects the large subunit of the bacterial ribosome, which is different from the large subunit of he human ribosome 225, Each of the following statements regarding the organisms’ normal flora is correct EXCEPT a.) The predominant organisms in the nose are acid- fast rods b.) The predominant organisms on the skin are coagulase negative staphylococci c.) The predominant organisms in the throat are gram- positive cocci in chains that form alpha- hemolytic colonies on d.) The predominant organisms in the colon are strict (obligate) anaerobes