Microbiology Quiz on Brucella and Enterobacteriaceae
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Questions and Answers

Brucella are gram-positive coccobacilli.

False (B)

Brucella melitensis is a common species that infects cattle.

False (B)

Brucellosis is also known as Malta fever and Bang disease.

True (A)

A typical treatment for Brucellosis involves a combination of tetracycline and penicillin.

<p>False (B)</p> Signup and view all the answers

Vaccines for brucella are not available for animals.

<p>False (B)</p> Signup and view all the answers

Legionnaires' disease is often contracted by women under 30 years of age.

<p>False (B)</p> Signup and view all the answers

The 1976 Legionnaires' disease outbreak in Philadelphia resulted in over 100 fatalities.

<p>False (B)</p> Signup and view all the answers

Azithromycin is a common treatment for infections caused by Enterobacteriaceae.

<p>False (B)</p> Signup and view all the answers

Enterobacteriaceae are primarily found in aquatic environments only.

<p>False (B)</p> Signup and view all the answers

Enterobacteriaceae are spore-forming gram-negative rods.

<p>False (B)</p> Signup and view all the answers

Enterobacteriaceae are a common cause of diarrhea primarily due to the production of endotoxins.

<p>False (B)</p> Signup and view all the answers

Enterobacteriaceae, along with Bacillus sp., contribute to approximately 50% of nosocomial infections.

<p>False (B)</p> Signup and view all the answers

All enteric bacteria can ferment glucose.

<p>True (A)</p> Signup and view all the answers

Enteric bacteria are oxidase positive.

<p>False (B)</p> Signup and view all the answers

Enteric bacteria are divided into coliforms which ferment lactase and non-coliforms which do not.

<p>False (B)</p> Signup and view all the answers

Enrichment, selective and differential media are used for isolating enteric bacteria.

<p>True (A)</p> Signup and view all the answers

All enteric bacteria produce hydrogen sulfide (H2S).

<p>False (B)</p> Signup and view all the answers

Enteric bacteria reduce nitrates to nitrites.

<p>True (A)</p> Signup and view all the answers

If an enteric bacterium is lactose negative, then it is also hydrogen sulfide negative.

<p>False (B)</p> Signup and view all the answers

All enteric bacteria are catalase negative.

<p>False (B)</p> Signup and view all the answers

Coliforms are non-lactose fermenters.

<p>False (B)</p> Signup and view all the answers

Klebsiella is positive for the Voges-Proskauer test.

<p>True (A)</p> Signup and view all the answers

Escherichia is negative for Lysine Decarboxylase (LDC).

<p>False (B)</p> Signup and view all the answers

Proteus is positive for Phenylalanine (PA).

<p>True (A)</p> Signup and view all the answers

Salmonella is gelatinase negative.

<p>False (B)</p> Signup and view all the answers

Morganella is negative for motility.

<p>True (A)</p> Signup and view all the answers

Hafnia is positive for ONPG.

<p>True (A)</p> Signup and view all the answers

Shigella is negative for gelatinase.

<p>True (A)</p> Signup and view all the answers

Erwinia is negative for the Voges-Proskauer (VP) test.

<p>False (B)</p> Signup and view all the answers

Citrobacter is positive for citrate.

<p>True (A)</p> Signup and view all the answers

Flashcards

What is Brucellosis?

A bacterial disease transmitted to humans from infected animals, typically cattle or pigs.

What kind of bacteria is Brucella?

Tiny, gram-negative bacteria with a coccobacillus shape.

What does the Agglutination Titer Test measure?

A diagnostic test for Brucellosis that measures the presence of antibodies against Brucella bacteria in a patient's blood serum.

What's a characteristic symptom of Brucellosis?

A fluctuating pattern of fever in Brucellosis patients that can last for weeks or even a year.

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How is Brucellosis typically treated?

A type of antibiotic used to treat Brucellosis infections, often combined with other drugs like rifampin or streptomycin.

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Aerobic bacteria

Bacteria that grow best in the presence of oxygen.

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Facultative anaerobes

Bacteria that can grow in the presence or absence of oxygen.

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Obligate anaerobes

Bacteria that can only grow in the absence of oxygen.

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Coliforms

A group of bacteria that can ferment lactose, producing acid and gas.

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Non-coliforms

Bacteria that can't ferment lactose.

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Glucose fermentation

A metabolic process that generates energy by breaking down glucose.

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Nitrate reduction

A process where bacteria break down nitrates into nitrites.

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Catalase

An enzyme that breaks down hydrogen peroxide.

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Oxidase

An enzyme that breaks down cytochrome c.

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What is Legionellosis?

A bacterial infection caused by Legionella pneumophila. It can cause pneumonia, fever, cough, diarrhea, abdominal pain, and even death. It was named after the American Legion, as an outbreak affected members at a 1976 convention in Philadelphia.

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What is Legionnaires' Disease?

A severe form of Legionellosis, often characterized by pneumonia, high fever, and respiratory distress.

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What is Pontiac Fever?

A milder form of Legionellosis, typically characterized by fever, headache, and muscle aches.

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What is Enterobacteriaceae?

A large family of Gram-negative bacteria that commonly inhabit the environment, including soil, water, and the intestines of animals.

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What are Facultative Anaerobes?

Able to survive with or without oxygen, meaning they can grow in both aerobic and anaerobic conditions.

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What does 'Nosocomial' mean?

Commonly occurring in hospitals or other healthcare settings.

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What is the significance of Enterobacteriaceae and Pseudomonas in hospitals?

These bacteria are responsible for nearly half of all infections occurring in healthcare settings.

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Rapid Lactose Fermentation on TSI

A rapid lactose fermentation on TSI indicates that the bacterium can utilize lactose for energy.

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Phenylalanine (PA) Test

A positive phenylalanine (PA) test indicates the presence of an enzyme that converts phenylalanine to phenylpyruvic acid, which reacts with ferric chloride to produce a green color.

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Indole Test

The Indole test detects the production of indole from tryptophan. A positive result is indicated by a red color after adding Kovac's reagent.

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Voges-Proskauer (VP) Test

The Voges-Proskauer (VP) test determines the production of acetoin from glucose. A positive result is indicated by a red color after adding VP reagents.

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H2S Test

A positive H2S test indicates the production of hydrogen sulfide gas, often seen as a black precipitate in the medium.

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Citrate Test

The Citrate test determines the ability of bacteria to utilize citrate as a sole carbon source. A positive result is indicated by a blue color change in the medium.

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Motility

Motility describes the ability of bacteria to move independently. This is observed by looking for a diffuse growth pattern in the medium.

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ONPG Test

The ONPG test detects the presence of an enzyme that cleaves ONPG, a synthetic substrate, into galactose and o-nitrophenol, producing a yellow color change in the medium.

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Urease Test

Urease is an enzyme that hydrolyzes urea, producing ammonia. This ammonia raises the alkalinity of the medium as indicated by a pink color change.

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Study Notes

Gram-Negative Bacilli of Medical Importance

  • Gram-negative bacilli are a diverse group of non-spore-forming bacteria.
  • They occupy various habitats, including the large intestine, respiratory tract, soil, water, and are zoonotic.
  • Many are not medically important, but some are true pathogens, while others are opportunistic pathogens.
  • All have an outer membrane lipopolysaccharide, which is endotoxin.

Learning Outcomes

  • Understanding and explaining the morphology and pathogenesis of pathogenic bacteria.
  • Evaluating the consequences of infection, treatment, and control of selected pathogenic bacteria.

Aerobic Gram-Negative Nonenteric Bacilli

  • This is a large, diverse group of non-spore-forming bacteria.
  • Exhibit a wide range of habitats (e.g. large intestines, zoonotic, respiratory, soil, water).
  • Most are not medically important; some are true pathogens, others are opportunists.
  • All have an outer membrane lipopolysaccharide (endotoxin) in their cell walls.

Pseudomonas and Burkholderia

  • Pseudomonas and Burkholderia are opportunistic pathogens.
  • Brucella and Francisella are zoonotic pathogens.
  • Bordetella and Legionella are primarily human pathogens.

Pseudomonas: The Pseudomonads

  • Small Gram-negative rods with a single polar flagellum.
  • Free-living in soil, sea water, and fresh water, commonly colonizing plants and animals.
  • Important decomposers and bioremediators.
  • Frequent contaminants in homes and clinical settings.
  • Utilize aerobic respiration; do not ferment carbohydrates.
  • Produce oxidase and catalase.
  • Many produce water-soluble pigments.

Pseudomonas aeruginosa

  • A common inhabitant of soil and water.
  • Found in 10% of normal people's intestines.
  • Resistant to soaps, dyes, quaternary ammonium disinfectants, drugs, and drying.
  • A frequent contaminant of ventilators, IV solutions, and anesthesia equipment.
  • An opportunistic pathogen.
  • A common cause of nosocomial infections in hosts with burns, neoplastic disease, cystic fibrosis.
  • Complications include pneumonia, UTIs, abscesses, otitis, and corneal disease.
  • Endocarditis, meningitis, and bronchopneumonia are other complications.
  • Exhibit a grape-like odor and greenish-blue pigment (pyocyanin).
  • Often multidrug-resistant.
  • Includes genera Burkholderia, Acinetobacter, Stenotrophomonas.
  • Similar to pseudomonads in characteristics.
  • Exhibit wide habitats in soil, water, and related environments.
  • Obligate aerobes; do not ferment sugars.
  • Motile and oxidase positive.
  • Opportunistic pathogens.

Burkholderia cepacia

  • Active in biodegradation of various substances.
  • Opportunistic agent in the respiratory tract, urinary tract, and occasionally skin infections.
  • Drug resistant.

B. pseudomallei

  • Generally acquired through penetrating injury or inhalation.
  • From environmental reservoirs.
  • Causes wound infections, bronchitis, pneumonia, and septicemia.

Acinetobacter baumannii

  • Causes nosocomial and community-acquired infections.
  • Affects wounds, lungs, urinary tract, burns, and blood.
  • Extremely resistant; treatment usually requires combination antimicrobials.

Stenotrophomonas maltophilia

  • Forms biofilms.
  • Contaminant of disinfectants, dialysis equipment, respiratory equipment, water dispensers, and catheters.
  • Clinical isolates frequently found in respiratory soft tissue, blood, and CSF.
  • High resistance to multidrugs.

Concept Check (Page 12)

  • The main reservoir for Pseudomonas aeruginosa is soil and water.

Brucella and Brucellosis

  • Tiny Gram-negative coccobacilli.
  • Two species, Brucella abortus (cattle) and Brucella suis (pigs).
  • Brucellosis (also known as Malta fever, undulant fever, and Bang disease) is a zoonotic disease transmitted to humans from infected animals.
  • Characterized by a fluctuating pattern of fever lasting weeks to a year.
  • Treatment usually involves a combination of tetracycline and rifampin, or streptomycin.
  • An animal vaccine is available.
  • A potential bioweapon.

Agglutination Titer Test for Brucellosis

  • Used to diagnose Brucellosis.
  • Measures antibody levels to Brucella.
  • A positive result shows antibodies reacting with Brucella cells.

Francisella tularensis and Tularemia

  • Causes tularemia, a zoonotic disease of mammals.
  • Endemic in the Northern Hemisphere, particularly rabbits.
  • Transmitted by contact with infected animals, water, or dust, or by insect vectors.
  • Symptoms include headache, backache, fever, chills, malaise, and weakness.
  • A 10% death rate in systemic and pulmonic forms.
  • Intracellular persistence can lead to relapse.
  • Treatment includes gentamicin or tetracycline.
  • An attenuated vaccine is available.
  • Potential bioterrorism agent.

Bordetella pertussis

  • Minute, encapsulated coccobacillus.
  • Causes pertussis (whooping cough), a communicable childhood affliction.
  • Causes an acute respiratory syndrome.
  • Often severe, life-threatening complications in babies.
  • Reservoir is apparently healthy carriers.
  • Transmission occurs by direct contact or inhalation of aerosols.

Bordetella pertussis - Virulence factors

  • Receptors that recognize and bind to ciliated respiratory epithelial cells.
  • Toxins that destroy and dislodge ciliated cells.
  • Loss of ciliary mechanism leads to mucus buildup and airway blockage.
  • Vaccine (DTaP) contains acellular vaccine (toxoid and other antigens).

Alcaligenes

  • Primarily found in soil and water.
  • May become normal flora.
  • A. faecalis – most common species isolated from feces, sputum, and urine.
  • Occasionally associated with opportunistic infections (pneumonia, septicemia, meningitis).

Legionella pneumophila and Legionellosis

  • Widely distributed in water.
  • Live in close association with amoebas.
  • 1976 epidemic of pneumonia afflicted 200 American Legion convention attendees in Philadelphia, killing 29.
  • Legionnaires disease and Pontiac fever.
  • Prevalent in males over 50.
  • Nosocomial disease in elderly patients.
  • Symptoms often include fever, cough, diarrhea, abdominal pain, and pneumonia (fatality rate of 3-30%).
  • Treatment includes azithromycin.

Enterobacteriaceae Family

  • Large family of small, non-spore-forming Gram-negative rods.
  • Many members inhabit soil, water, and decaying matter.
  • Common occupants of the large bowel of animals (including humans).
  • Most frequent cause of diarrhea through enterotoxins.
  • Enterics along with Pseudomonas sp. account for almost 50% of nosocomial infections.
  • Facultative anaerobes, grow best in air.
  • All ferment glucose, reduce nitrates to nitrites, oxidase negative, catalase positive.
  • Divided into coliforms (lactose fermenters) and noncoliforms (non-lactose fermenters).
  • Enrichment, selective, and differential media often utilized for screening samples for pathogens.

The Enteric Genera (Page 23)

  • Gram-negative rods identified based on a series of biochemical tests allowing for rapid identification using selective media and different tests such as lactose-fermentation tests and motility.

BBL Enterotube II, Rapid Biochemical Testing of Enterics (Page 24)

  • A commercial system for rapid biochemical identification of common opportunistic enterics using IMVIC tests.

Antigen Structures and Virulence Factors (Page 25)

  • Complex surface antigens contribute to pathogenicity and trigger immune responses.
  • H – flagellar antigen,
  • K – capsule antigen, or fimbrial antigen,
  • O – somatic or cell wall antigen.
  • Endotoxin
  • Exotoxins displayed by various pathogenic microorganisms.

Concept Check (Page 26)

  • All of the above are true regarding the enterics: some are normal flora, some release endotoxins, and some release enterotoxins.

Escherichia coli: The Most Prevalent Enteric Bacillus

  • Most common aerobic and nonfastidious bacterium in the gut.
  • 150 strains are recognized, including some with virulence factors due to plasmid transfer, and some are opportunistic.

Pathogenic Strains of E. coli

  • Enterotoxigenic E. coli (ETEC) – causes severe diarrhea due to heat-labile toxin and heat-stable toxin – stimulating secretion.
  • Enteroinvasive E. coli (EIEC) – causes inflammatory disease in the large intestine.
  • Enteropathogenic E. coli (EPEC) – linked to wasting form of infantile diarrhea.
  • Enterohemorrhagic E. coli (EHEC), O157:H7 strain – causes hemorrhagic syndrome and kidney damage.

Escherichia coli

  • Pathogenic strains of E. coli are frequent agents of infantile diarrhea.
  • Often a major cause of mortality among babies.
  • Causes approximately 70% of traveler's diarrhea.
  • Responsible for 50–80% of UTIs.
  • Coliform count is an indicator of fecal contamination in water.

Klebsiella pneumoniae

  • Normal inhabitant of the respiratory tract.
  • Has a large capsule.
  • Causes nosocomial pneumonia, meningitis, bacteremia, wound infections, and UTIs.

Opportunistic Coliforms

  • Enterobacter sp. – UTIs, surgical wounds.
  • Citrobacter sp. – opportunistic UTIs and bacteremia.
  • Serratia marcescens – produces a red pigment, causes pneumonia, burn and wound infections, septicemia.

Noncoliform Lactose-Negative Enterics

  • Proteus, Morganella, Providencia.
  • Salmonella and Shigella.

Opportunists: Proteus and Its Relatives

  • Ordinarily harmless saprobes in soil, manure, sewage, polluted water, and commensals of humans and animals.
  • Proteus sp. – swarm on the surface of moist agar in a concentric pattern and are involved in UTIs, wound infections, pneumonia, septicemia, and infant diarrhea.
  • Morganella morganii and Providencia sp. are also involved in similar infections.

Salmonella and Shigella

  • Well-developed virulence factors.
  • Primary pathogens, not normal human flora.
  • Salmonelloses and Shigelloses – some gastrointestinal involvement and diarrhea but often affecting other systems.

Typhoid Fever and Other Salmonelloses

  • Salmonella typhi is the most serious pathogen of the genus, causing typhoid fever; human host.
  • S. cholerae-suis is a zoonosis of swine.
  • S. enteritidis includes 1,700 different serotypes, based on variation in O, H, and V.
  • Flagellated and survive out of the host.
  • Resistant to chemicals, like bile and dyes.

Typhoid Fever

  • Bacillus enters via ingestion of fecally contaminated food or water.
  • Occasionally spread by close personal contact.
  • Asymptomatic carriers; some chronic carriers shed bacilli from the gallbladder.
  • Bacilli adhere to the small intestine and cause invasive diarrhea, leading to septicemia.
  • Treated with chloramphenicol or sulfamethoprim.
  • 2 vaccines available for temporary protection.

Animal Salmonelloses

  • Salmonelloses other than typhoid fever are called enteric fevers, Salmonella food poisoning or gastroenteritis.
  • Usually less severe than typhoid fever, but more prevalent.
  • Caused by one of many serotypes of Salmonella enteritidis; all zoonotic in origin, though humans can become carriers.
  • Commonly found in cattle, poultry, rodents, reptiles, and dairy products.
  • Fomites contaminated with animal intestinal flora.

Shigella and Bacillary Dysentery

  • Shigellosis (incapacitating dysentery) can be caused by S. dysenteriae, S. sonnei, S. flexneri, and S. boydii.
  • Invades the villi of the large intestine but does not perforate the intestine or invade blood.
  • Enters Peyer's patches and instigates an inflammatory response.
  • Treatment involves fluid replacement and ciprofloxacin or sulfamethoprim.

The Enteric Yersinia Pathogens

  • Yersinia enterocolitica: affects domestic and wild animals; fish; fruits; vegetables; and water.
  • Bacteria enter the small intestinal mucosa and some enter lymphatic tissue and survive in phagocytes.
  • Inflammation of the ileum can mimic appendicitis.
  • Yersinia pseudotuberculosis causes an infection similar to Y. enterocolitica, though with more lymph node inflammation.

Nonenteric Yersinia pestis and Plague

  • Nonenteric; tiny Gram-negative rod with unusual bipolar staining and capsules.
  • Virulence factors include capsular and envelope proteins, which protect against phagocytosis and foster intracellular growth.
  • Exhibits coagulase, endotoxin, and murine toxin.

Yersinia pestis

  • Humans develop plague through contact with wild animals (sylvatic plague) or domestic or semidomestic animals (urban plague) or infected humans.
  • Found in 200 species of mammals including rodents, however, without causing disease.
  • Flea vectors – bacteria replicates in the gut, coagulase causes blood clotting that blocks the esophagus - flea becomes ravenous.

Infection Cycle of Yersinia pestis

  • The infection cycle involves endemic reservoir hosts (e.g. rodents), amplifying hosts (e.g. ground squirrels), and human (accidental) hosts (humans getting sick from contact with rodents).

Pathology of Plague

  • ID 3-50 bacilli.
  • Bubonic - bacillus multiplies in flea bite, enters lymph; causes necrosis and swelling called a bubo in groin or axilla.
  • Septicemic - progression to massive bacterial growth; virulence factors cause intravascular coagulation; subcutaneous hemorrhage and purpura (black plague).
  • Pneumonic - infection localized to lungs, highly contagious; fatal without treatment.

Diagnosis, Treatment, and Prevention of Plague

  • Diagnosis depends on history, symptoms, and laboratory findings from aspiration of buboes.
  • Treatment includes streptomycin, tetracycline, or chloramphenicol.
  • A killed or attenuated vaccine is available.
  • Prevention involves quarantine and control of rodent populations in human habitats.

Oxidase-Positive Nonenteric Pathogens

  • Pasteurella multocida
  • Haemophilus influenzae
  • H. aegyptius
  • H. ducreyi
  • H. parainfluenzae
  • H. aphrophilus.

Pasteurella multocida

  • Zoonotic genus; normal flora in animals.
  • Opportunistic infections.
  • Animal bites or scratches cause local abscesses; infection can spread to joints, bones, and lymph nodes.
  • Immunocompromised are at risk for septicemia and complications.
  • Treatment: penicillin and tetracycline.

Haemophilus

  • Tiny Gram-negative pleomorphic rods.
  • Fastidious, sensitive to drying and temperature extremes, and disinfectants.
  • None can grow on blood agar, require special techniques (e.g. chocolate agar).
  • Require hemin, NAD or NADP.
  • Some species are normal colonists of the upper respiratory tract or the vagina.
  • Virulent species are responsible for childhood meningitis and chancroid.

Haemophilus influenzae

  • Acute bacterial meningitis, epiglottitis, otitis media, sinusitis, pneumonia, bronchitis.
  • Subunit vaccine (Hib) available.

Haemophilus aegyptius

  • Conjunctivitis (pink eye).

Haemophilus ducreyi

  • Chancroid STD.

Haemophilus parainfluenzae and H. aphrophilus

  • Normal oral and nasopharyngeal flora.
  • Infective endocarditis.

Systems Profile 20.1 Pathogenic Gram-Negative Bacilli (Page 51)

  • A table summarizing information about the Gram-negative bacteria and the systems they affect.

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Test your knowledge on the characteristics and treatments of Brucella and Enterobacteriaceae. This quiz covers topics such as brucellosis and Legionnaires' disease, as well as the classification of enteric bacteria. Challenge yourself with questions related to these important microorganisms and their impact on health.

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