Home Books Jawetz, Melnick, & Adelberg’s Medical Microbiology, 27e

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

Acinetobacter species:

(A) Are only found in a hospital environment.

(B) May appear as Gram-positive rods.

(C) Can mimic the morphology of Hemophilus species in Gram stains of endocervical secretions.

(D) Can be a significant cause of ventilator-associated pneumonia in intensive care unit patients.

(E) Are susceptible to most antibiotics.

A 37-year-old firefighter sustains smoke inhalation and is hospitalized for ventilatory support. He has a severe cough and begins to expectorate purulent sputum. Gram stain of his sputum specimen shows numerous polymorphonuclear cells and numerous Gram-negative rods. Sputum culture grows numerous Gram-negative rods that are oxidase positive. They grow well at 42°C. On clear agar medium, they produce a green color in the agar. The agar where the green color is located fluoresces when exposed to ultraviolet light. The organism causing the patient’s infection is

(A) Pseudomonas aeruginosa

(B) Klebsiella pneumoniae

(C) Escherichia coli

(D) Burkholderia cepacia

(E) Burkholderia pseudomallei

The mechanism of action of exotoxin A of Pseudomonas aeruginosa is

(A) To activate acetylcholine esterase

(B) To block elongation factor 2

(C) To form pores in white blood cells and increase cation permeability

(D) To increase intracellular cyclic adenosine monophosphate

(E) To split lecithin into phosphorylcholine and diacylglycerol

Patients deficient in these cells are at high risk for developing serious systemic infections with Pseudomonas aeruginosa:

(A) Eosinophils

(B) Neutrophils

(C) Macrophages

(D) Natural killer cells

(E) CD4+ T cells

A marine wounded in Afghanistan returns to her home a paraplegic. Her past medical history included surgery to amputate both her legs below the knee and the placement of a suprapubic tube to repair damage to her bladder. She is now at the VA outpatient clinic with a recurrent urinary tract infection that has not responded to conventional antibiotic regimens for community-acquired cystitis. Her urine is positive for small, plump Gram-negative coccobacilli. When cultured, this organism does not ferment carbohydrates, does not hydrolyze urea, does not reduce nitrates, and does not make hydrogen sulfide. The organism most likely causing this marine’s infection is:

(A) Klebsiella oxytoca

(B) Escherichia coli

(C) Staphylococcus saprophyticus

(D) Proteus mirabilis

(E) Acinetobacter baumanii

A 70-year-old neutropenic patient was diagnosed with ecthyma gangrenosum 3 days after he developed a fever of 39°C. Blood cultures drawn the day his fever started grew out overnight a strictly aerobic, Gram-negative rod that was lactose negative and oxidase positive. Which of the following antibiotic regimens would be most appropriate for treating this patient?

(A) Tobramycin + piperacillin/tazobactam

(B) Vancomycin + metronidazole

(C) Cefazolin

(D) Tigecycline

(E) Oxacillin

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Chapter 16: Pseudomonads and Acinetobacter

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Chapter 16: Pseudomonads and Acinetobacter

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