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Enterobacteriaceae
Characteristics of the enterics and their biochemical tests.
52
Microbiology
Undergraduate 3
07/13/2013

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Term
When organisms that possess urease hydrolyze urea, what product is released?
Definition
Ammonia
Term
What is the only oxidase-negative, lactose-positive organism that is H2S-positive?
Definition
Citrobacter freundii
Term
This organism produces a deadly, bloody diarrhea often associated with Haemolytic Uremic Syndrome (HUS).
Definition
Enterohaemorrhagic E. coli (EHEC)
Term
What is the Gram stain reaction and morphology common to all Enterobacteriaceae?
Definition
Gram-negative rods or coccobacilli
Term
What is the only genus in Enterobacteriaceae that is oxidase-positive?
Definition
Plesiomonas
Term
Name two organisms that are oxidase-negative, lactose-negative, and H2S-negative.
Definition
Shigella and Yersinia
Term
What three genera of Enterobacteriaceae are non-motile?
Definition
Klebsiella, Shigella, and Yersinia.
Term
True/False: Enterobacteriaceae are non-spore-forming.
Definition
True
Term
What organism is Sorbitol-MacConkey agar selective and differential for?
Definition
Enterohaemorrhagic Escherichia coli (EHEC) serotype O157:H7
Term
Does Salmonella produce H2S?
Definition
Yes
Term
What organism in Enterobacteriaceae produces severe, often fatal pneumonia?
Definition
Klebsiella pneumoniae
Term
Which heat-stable bacterial antigen is found in the cell wall and stimulates early antibody production?
Definition
O antigen
Term
Which organism is oxidase-negative, lactose-positive, H2S-positive, and indole-negative?
Definition
Citrobacter freundii
Term
True/False: Members of Enterobacteriaceae are uniformly obligate aerobes.
Definition
False - they are uniformly facultative anaerobes.
Term
How do Salmonella and Shigella appear differently on Hektoen enteric (HE) agar and what produces that difference?
Definition
Shigella appears green; Salmonella appears black because it produces H2S.
Term
Aside from Proteus mirabilis, what organism is oxidase-negative, lactose-negative, H2S-positive, and indole-negative?
Definition
Salmonella spp.
Term
What color will a lactose fermenter appear on MAC?
Definition
Pink
Term
Which heat-labile bacterial antigen is found on the flagella and stimulates late antibody production?
Definition
H antigen
Term
What must be added to any negative tube in a nitrate test?
Definition
Zinc dust
Term
What is the main way to differentiate Enterobacter from Klebsiella?
Definition
Enterobacter is motile; Klebsiella is non-motile.
Term
What is the IMViC profile of Citrobacter?
Definition
= + = +
Term
Will TSI agar show H2S production?
Definition
Yes
Term
Kovac's reagent is used for which biochemical test?
Definition
Indole
Term
What is the IMViC profile of Serratia spp.?
Definition
= = + +
Term
What is the key biochemical test difference between P. mirabilis and P. vulgaris?
Definition
Indole - P. mirabilis is negative; P. vulgaris is positive
Term
What organism exhibits bipolar or "safety pin" staining on a Gram stain?
Definition
Yersinia spp.
Term
What is the key biochemical test to differentiate Citrobacter from Salmonella?
Definition
Lysine decarboxylase; Citrobacter is negative and Salmonella is positive.
Term
What organism causes traveler's diarrhoea?
Definition
Enterotoxigenic E. coli (ETEC)
Term
Which of the following organisms is urease negative: Proteus mirabilis, Escherichia coli, or Klebsiella spp.?
Definition
Escherichia coli
Term
Which two organisms are the most common bacterial causes of UTIs?
Definition
Escherichia coli and Klebsiella pneumoniae
Term
Which of the following specimens is not appropriate for anaerobic culture: amniotic fluid, peritoneal fluid, sinus aspirate?
Definition
Peritoneal fluid
Term
What two oxidase-negative, lactose-negative organisms are H2S-positive?
Definition
Proteus and Salmonella
Term
What does a yellow butt on TSI indicate?
Definition
Glucose fermentation
Term
How can you differentiate Salmonella from Shigella based on motility?
Definition
Salmonella is motile and Shigella is non-motile.
Term
What color will a lactose fermenter appear on Hektoen enteric (HE) agar?
Definition
Orange or salmon
Term
What bacterial antigen is heat-labile, made of polysaccharide, and found only in encapsulated species?
Definition
K antigen
Term
What is the IMViC profile of Klebsiella?
Definition
= = + + (except K. oxytoca, which is + = + +)
Term
What characteristic color are Serratia marcescens colonies?
Definition
Red
Term
What organism caused the "Black Death" plague?
Definition
Yersinia pestis
Term
Aside from Salmonella, which organism is oxidase-negative, lactose-negative, H2S-positive, and indole-negative?
Definition
Proteus mirabilis
Term
What does a yellow slant on TSI agar indicate?
Definition
Lactose or sucrose fermentation
Term
What organisms are the two most common causes of bacterial diarrhea?
Definition
Salmonella and Campylobacter
Term
What is the IMViC profile of Enterobacter?
Definition
IMViC: = = + +
Term
Which one of the following genera is lactose positive: Salmonella, Providencia, Klebsiella, or Proteus?
Definition
Klebsiella
Term
Which carbohydrates are present in a triple sugar iron (TSI) agar?
Definition
Glucose (dextrose), lactose, and sucrose
Term
What color indicates a positive result in a lysine decarboxylase test?
Definition
Purple
Term
What two things does Hektoen enteric (HE) agar show?
Definition
Lactose fermentation and hydrogen sulfide (H2S) production.
Term
Which organism is oxidase-negative, lactose-positive, H2S-negative, indole-positive?
Definition
Escherichia coli
Term
Which organism ferments lactose slowly and is associated with nosocomial infections?
Definition
Citrobacter freundii
Term
Which non-motile, lactose-negative organism grows highly mucoid colonies on BAP and MAC, and has a "yeasty" odour?
Definition
Klebsiella spp.
Term
Swarming motility on culture plates is characteristic of which organism?
Definition
Proteus spp.
Term
Aside from Shigella sonnei, which organism is oxidase-negative, lactose-negative, H2S-negative, and indole-negative?
Definition
Yersinia spp.
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