Question 1

Which of the following is a distinguishing feature of Pseudomonas aeruginosa that contributes to its ability to survive in hospital environments?

Accepted Answer

It is resistant to soaps, dyes, and quaternary ammonium disinfectants

Question 2

A patient with cystic fibrosis develops pneumonia after prolonged hospitalization. Which Gram-negative bacillus is most likely responsible, and what pigment does it produce?

Accepted Answer

Pseudomonas aeruginosa; greenish-blue pigment (pyocyanin)

Question 3

Which of the following genera is an obligate aerobe, motile, oxidase positive, and does not ferment sugars?

Accepted Answer

Burkholderia

Question 4

A cancer patient with an indwelling catheter develops a drug-resistant infection. The isolate forms biofilms and is best treated with trimethoprim-sulfamethoxazole. Which organism is most likely responsible?

Accepted Answer

Stenotrophomonas maltophilia

Question 5

Brucella abortus is primarily associated with which animal, and what is the characteristic pattern of fever in human brucellosis?

Accepted Answer

Cattle; undulant (fluctuating) fever

Question 6

Which of the following best describes the transmission route and main symptoms of tularemia caused by Francisella tularensis?

Accepted Answer

Contact with infected animals or vectors; ulcerative skin lesions and swollen lymph glands

Question 7

Bordetella pertussis causes whooping cough primarily by which mechanism?

Accepted Answer

Binding to ciliated respiratory epithelial cells and releasing toxins that destroy cilia

Question 8

Which of the following is a key virulence factor of enteric bacteria that can trigger endotoxic shock?

Accepted Answer

O antigen (somatic/cell wall)

Question 9

A traveler develops severe diarrhea after eating street food. The causative agent is a Gram-negative rod that produces both heat-labile and heat-stable toxins. Which pathotype of E. coli is most likely responsible?

Accepted Answer

Enterotoxigenic E. coli (ETEC)

Question 10

Which of the following enteric bacteria is most commonly associated with hemolytic uremic syndrome following consumption of undercooked beef?

Accepted Answer

Escherichia coli O157:H7

Question 11

Which enzyme is responsible for carbapenem resistance in Klebsiella pneumoniae?

Accepted Answer

KPC (Klebsiella pneumoniae carbapenemase)

Question 12

A patient presents with acute diarrhea and a history of cleaning a pet snake’s aquarium. Which pathogen is most likely responsible?

Accepted Answer

Salmonella bongori

Question 13

Which of the following best describes the pathology of bubonic plague caused by Yersinia pestis?

Accepted Answer

Enlarged (swollen) lymph node

Question 14

Legionella pneumophila is most commonly associated with which environmental reservoir and what is the most severe disease it causes?

Accepted Answer

Water and amoebas; Legionnaires’ disease

Question 15

Which of the following is a key laboratory characteristic used to differentiate members of the family Enterobacteriaceae?

Accepted Answer

Glucose fermentation

Question 16

Which of the following is true regarding the antigenic structure of enteric bacteria?

Accepted Answer

Only O antigen is present in all species

Question 17

A patient develops pneumonia after exposure to contaminated water in a hospital. The causative agent is not contagious and is best treated with levofloxacin. Which organism is most likely responsible?

Accepted Answer

Legionella pneumophila

Question 18

Which of the following is a common complication of infection with Klebsiella pneumoniae in hospital settings?

Accepted Answer

Nosocomial pneumonia

Question 19

Which of the following best explains why Stenotrophomonas maltophilia is difficult to eradicate from hospital equipment?

Accepted Answer

It forms biofilms that protect it against drugs and disinfectants

Question 20

Which of the following equations best represents the calculation of the infectious dose (ID) for Yersinia pestis, given that the minimum number of bacilli required to cause infection is between 3 and 50?

Accepted Answer

$$ID_{range} = [3, 50]$$

Chapter 20: The Gram-Negative Bacilli of Medical Importance

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