2. A76-year-old man with atherosclerosis had been previously admitted for abdomi

Question

2. A76-year-old man with atherosclerosis had been previously admitted for abdominal aneurysm and resection of the perirenal aorta. He had several follow-up admissions over the next year for postoperative wound infections, with accompanying bacteremia, alternating between Pseudomonas aeruginosa, vancomycin-resistant Enterococcus faecium, and Candida glabrata. On his final admission, blood cultures were positive, with numerous gram-positive cocci in pairs and chains in the smear, but subculture of the bottle showed no growth aerobically with increased CO2 on blood agar or chocolate agar or anaerobically on Brucella agar. QUESTIONS a) What is this organism and what would you do to grow it? b) To control infection, screening for vancomycin resistance in enterococci on selected hospitalized patients is important. What is a cost-effective screening method? c) Many genera of gram-positive cocci are catalase negative, but only a few are vancomycin-resistant. Name these genera, and indicate how they can be differentiated from vancomycin-resistant enterococci.

Explanation / Answer

2)

a) The organism in question is Enterococcus faecium. They can be grown in 6.5% sodium chloride solution.

b) Cost effective screening methods for vancomycin resistant enterococci are Brain heart infusion agar supplemented with 6 micrograms of vancomycin per ml and Direct plating of triplet rectal swab onto Bd Vancomycin Resitant Enterococci Selective Agar (Japan Becton Dickson).

c) Gram positive cocci, catalase negative:

Vancomycin resistant gram positive cocci:

Leuconostoc species produces carbondioxide during fermentation of glucose. This property distinguishes them enterococcus which do not produce carbondioxide on fermenting glucose.

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