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