Division of Infectious Diseases

December 2017

A 76 year old man with hypertension, type 2 diabetes, hyperlipidemia, benign prostatic hyperplasia, and a cholecystectomy 10 years ago presented for evaluation of a mass in the common bile duct.  A diagnostic laparascopy was done.  Cultures were sent, but labelled only "body fluid".  Gram stain showed no organisms and 1+ PMNs.  Few Gram-negative rods grew, with a very mucoid appearance.  Susceptibility results by automated methods showed resistance to cefoxitin but susceptibility to many other beta-lactams. The technologist was concerned and thought that the mucoid isolate may be producing inaccurate results.  Clearer results were obtained by disk diffusion, showing resistance to most beta-lactams except cefepime and meropenem (top figure). The disk diffusion plate was incubated for another 24 hours (bottom figure). The organisms then demonstrated many small colonies inside the zones of inhibition, except for cefepime and meropenem. 

What type of resistance mechanism is being demonstrated?  How can this be confirmed? 

Bauer-Kirby plate of bacteria identified as Enterobacter aerogenes.  Resistance to cefoxitin was seen by 24 hours (Figure 1), and by 48 hours (Figure 2) small colonies grew inside the zone of inhibition of other beta-lactams (red arrow at ceftriaxone), but not cefepime (FEP) or meropenem (not shown). 

Decemebr 2017December 2017a

Conferences & Seminars

Infectious Diseases Grand Rounds @ Einstein
Fellow's Presentation and Journal Club
Drs. Quintero, Zielinski and Mogollon
Wednesday, February 21, 2018 @ 8:30 AM

Conference & Seminar Schedules

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