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Chapter 16: Pseudomonads and Acinetobacter

A sputum culture of a patient with cystic fibrosis grows Pseudomonas aeruginosa that forms very mucoid colonies. The implication of this observation is which one of the following?

(A) The Pseudomonas aeruginosa is highly susceptible to the aminoglycoside antimicrobial tobramycin.

(B) The Pseudomonas aeruginosa is infected with a pyocin (a bacteriocin).

(C) The colonies are mucoid because they have polysaccharide capsule of hyaluronic acid.

(D) The exotoxin A gene has been disabled and the Pseudomonas aeruginosa is no longer able to block host cell protein synthesis.

(E) The Pseudomonas aeruginosa has formed a biofilm in the patient’s airway.

An environmental Gram-negative bacillus that is resistant to cephalosporins, aminoglycosides, and quinolones has become a very important nosocomial pathogen largely because it is selected by use of those antibiotics. This Gram-negative bacillus can take 2–3 days to grow and must be differentiated from Burkholderia cepacia. It is

(A) Pseudomonas aeruginosa

(B) Acinetobacter baumannii

(C) Alcaligenes xylosoxidans

(D) Klebsiella pneumoniae

(E) Stenotrophomonas maltophilia

A 17-year-old girl with cystic fibrosis has a slight increase in her frequent cough and production of mucoid sputum. A sputum specimen is obtained and plated on routine culture media. The predominant growths are Gram-negative bacilli that form very mucoid colonies after 48 hours of incubation. These bacilli are oxidase positive, grow at 42°C, and have a grapelike odor. These Gram-negative bacilli are which of the following?

(A) Klebsiella pneumoniae

(B) Pseudomonas aeruginosa

(C) Staphylococcus aureus

(D) Streptococcus pneumoniae

(E) Burkholderia cepacia

The sputum from a 26-year-old patient with cystic fibrosis is plated on a colistin-containing agar. After 72 hours of incubation, the colistin-containing agar grows Gram-negative bacilli that are oxidase positive but are otherwise difficult to identify. This microorganism is of major concern. It is sent to a reference laboratory so that molecular methods can be used to identify or rule out which of the following?

(A) Pseudomonas aeruginosa

(B) Burkholderia cepacia

(C) Haemophilus influenzae

(D) Pseudomonas putida

(E) Burkholderia pseudomallei


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