Question 1

Which of the following characteristics distinguishes Enterobacteriaceae from Pseudomonads in laboratory testing?

Accepted Answer

Enterobacteriaceae are oxidase negative, while Pseudomonads are oxidase positive.

Question 2

A patient presents with bloody, mucoid diarrhea and seizures. Which pathogen is most likely responsible, and what is the minimum infectious dose?

Accepted Answer

Shigella dysenteriae; minimum infectious dose is 50-200 cells.

Question 3

Which virulence factor of Enterobacteriaceae is responsible for triggering a strong immune response and is used for serotyping?

Accepted Answer

O antigen (outer membrane polysaccharide)

Question 4

A burn patient develops a wound infection with a greenish-blue pigment and a grapelike odor. Which organism is most likely responsible, and what is the pigment called?

Accepted Answer

Pseudomonas aeruginosa; pigment is pyocyanin.

Question 5

Which Enterobacteriaceae member is most commonly associated with neonatal meningitis due to its K1 antigen?

Accepted Answer

Escherichia coli

Question 6

On a Triple Sugar Iron (TSI) agar, which result indicates a non-lactose fermenting, H2S-producing organism?

Accepted Answer

K/A, H2S

Question 7

Which equation best describes the relationship between the number of bacteria and the probability of infection for Shigella, given its low infectious dose?

Accepted Answer

$$P = 1 - e$$^{-kN}$$, where P$ is probability, N$ is number of bacteria, k$ is a constant

Question 8

Which of the following is a major cause of nosocomial pneumonia and is known for its large capsule and resistance to carbapenems?

Accepted Answer

Klebsiella pneumoniae

Question 9

Which Enterobacteriaceae member is most frequently associated with bacteremia, according to epidemiological data?

Accepted Answer

Escherichia

Question 10

A patient with cystic fibrosis develops a respiratory infection with a mucoid capsule and resistance to multiple antibiotics. Which organism is most likely responsible?

Accepted Answer

Pseudomonas aeruginosa

Question 11

Which pathogenic E. coli strain is most likely to cause hemolytic uremic syndrome and produces a shiga-like toxin?

Accepted Answer

Enterohemorrhagic E. coli (EHEC)

Question 12

Which of the following is NOT a recommended method for preventing gastrointestinal infections while traveling?

Accepted Answer

Consume ice in drinks

Question 13

Which Enterobacteriaceae member is known for swarming motility on moist agar and is resistant to many antibiotics?

Accepted Answer

Proteus species

Question 14

Which virulence factor allows Yersinia pestis to evade phagocytosis and grow intracellularly?

Accepted Answer

Capsule and envelope proteins

Question 15

A patient presents with appendicitis-like pain after eating contaminated vegetables. Which organism is most likely responsible?

Accepted Answer

Yersinia enterocolitica

Question 16

Which of the following is a primary pathogen and NOT a normal part of human flora?

Accepted Answer

Salmonella enterica

Question 17

Which equation represents the calculation of coliform count as an indicator of fecal contamination?

Accepted Answer

$$C = \frac{N_{coliform}}{V_{sample}}$$, where $$C is $$coliform count, $$N_{coliform} is $$number of coliforms, $$V_{sample} is $$sample volume

Question 18

Which Enterobacteriaceae member is associated with genital granulomas (donovanosis) and treated with macrolides?

Accepted Answer

Klebsiella granulomatis

Question 19

Which of the following is a major virulence factor of Pseudomonas aeruginosa that blocks translation elongation in host cells?

Accepted Answer

Exotoxin A

Question 20

Which mode of transmission is NOT included in the '5 Fs' for gastrointestinal infection prevention?

Accepted Answer

Fur

Enterobacteriaceae and Pseudomonads: Structure, Pathogenesis, and Clinical Relevance

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