Objective: To identify CPE and define the epidemiology of and risk factors for these organisms in a tertiary care hospital in Baltimore.
Methods: Starting in October 2007, all Enterobacteriaceae except Proteus sp., Morganella morganii, and Providencia sp. were screened for carbapenemase production. Initial identification and susceptibility testing was performed using
Results: Over an 18 month period, 245 unique isolates contributed by 114 patients met our criteria for testing by MHT. Ninety-eight (40%) were MHT positive: Enterobacter sp. 66/149(44.3%), Klebsiella sp. 24/58(41.4%), Citrobacter sp. 5/17(29.4%), Serratia sp. 1/4 (25%), and E. coli 2/17 (11.8%). 97 MHT positive isolates were tested by PCR and 87(89.7%) were confirmed as KPC2. Among KPC2-PCR positive isolates, 74% were tigecycline susceptible and 93% had colistin MICs of <= 1ug/ml. The average age of case patients in the study was 57.4 years and 45% were female. 19 (43%) case patients grew CPE from cultures of sputum, 12 (27%) grew it in urine, and 4 patients had bacteremia. 52% of the case patients died during the hospitalization compared with 11% of the controls (p<.001). Severity of illness assessed with a modified APACHE III score (OR=1.06, CI 1.01-1.09)) and solid organ transplantation (OR=5.34, CI 1.3-22) were independent risk factors for CPE acquisition after controlling for receipt of broad spectrum antimicrobial agents.
Conclusions: CPE occur in our hospital among a variety of different species, primarily Enterobacter sp. in contrast to other locales reporting Klebsiella as the primary isolates. Case patients had a high crude mortality. Solid organ transplantation was a significant, independent risk factor for CPE acquisition. Screening for CPE with MHT is important to identify organisms that would otherwise not be recognized.