Carriage rate of carbapenem-resistant Klebsiella pneumoniae in hospitalised patients during a national outbreak

Abstract

During a national outbreak of carbapenem-resistant Klebsiella pneumoniae (CRKP) in Israel, we conducted a point prevalence survey to determine the extent of asymptomatic carriage. Subsequently, a retrospective case-control study was done, comparing carriers of CRKP with non-carriers, in order to detect risk factors for carriage. Oral, perianal and rectal swabs were obtained from all hospitalised eligible and consenting patients. Selective media for carbapenem-resistant Gram-negative bacteria were used and pulsed-field gel electrophoresis (PFGE) helped to determine clonal source. Culture was obtained from 298 patients. Sixteen (5.4%) were carriers of CRKP, with a higher carriage rate in medical and surgical wards. Only 18% of carriers were treated with any carbapenem prior to the survey. Five of the 16 carriers had a positive clinical specimen for CRKP, hence a clinical infection versus asymptomatic carriage ratio of 1:3. The rectum was the most sensitive site sampled, detecting 15/16 carriers, and the overall sensitivity of the method was 94% with a negative predictive value of 99.6%. In a multivariate analysis of risk factors for CRKP carriage, three variables were significantly related to carriage state: diaper use, longer duration of hospital stay and vancomycin use. PFGE demonstrated that all 16 isolates were identical, confirming clonal origin. A point prevalence survey performed at a single medical centre during an outbreak of CRKP demonstrated a carriage rate of 5.4%. The clonal origin of these isolates suggests that strict adherence to isolation procedure may contain this outbreak.