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Chapter 16: Pseudomonads and Acinetobacter

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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?

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

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

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

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

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

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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

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(A) Pseudomonas aeruginosa

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(B) Acinetobacter baumannii

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(C) Alcaligenes xylosoxidans

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(D) Klebsiella pneumoniae

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(E) Stenotrophomonas maltophilia

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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?

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(A) Klebsiella pneumoniae

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(B) Pseudomonas aeruginosa

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(C) Staphylococcus aureus

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(D) Streptococcus pneumoniae

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(E) Burkholderia cepacia

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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?

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(A) Pseudomonas aeruginosa

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(B) Burkholderia cepacia

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(C) Haemophilus influenzae

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(D) Pseudomonas putida

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(E) Burkholderia pseudomallei

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