Detection and characterization of extended-spectrum beta-lactamase-producing Enterobacteriaceae in high-risk patients in an Irish tertiary care hospital

Abstract

Extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-E) are Gram-negative, multi-drug-resistant organisms that are of major clinical significance among immunocompromised patients in high-risk areas in hospital settings. In Ireland, the number of ESBL-E bloodstream infections is increasing. To conduct a prevalence study of ESBL-E among immunocompromised patients in high-risk areas [intensive care unit (ICU), liver transplantation and haematology/oncology wards], characterize any ESBL genes detected by polymerase chain reaction (PCR), and perform epidemiological typing using pulsed-field gel electrophoresis (PFGE). In total, 317 non-duplicate rectal swabs from patients in high-risk wards were screened anonymously for ESBL-E carriage. Positive isolates were characterized using PCR to detect blaCTX-M, blaTEM, blaOXA-1 and blaSHV ESBL-E genes. Clonal relationships of these isolates were investigated using PFGE. Fifty (15.8%) high-risk patients were found to harbour ESBL-E. Prevalence rates of 21.9% (N=28), 14.3% (N=15) and 8.3% (N=7) of ESBL-E were isolated from patients on the liver transplantation, ICU and haematology/oncology wards, respectively. Seventy percent of ESBL-E isolates carried more than one resistance gene. Of the 25 ESBL-producing Escherichia coli isolates typed by PFGE, two pairs of two isolates demonstrated >80% homology, and four of the five ESBL-producing Enterobacter cloacae isolates typed by PFGE demonstrated >80% homology, suggesting clonal relatedness and potential cross-transmission from individual patients. A significant proportion of the patients screened were found to be colonized with ESBL-E. Typing revealed three incidents of potential cross-infection. Therefore, timely detection of ESBL-E among patients in high-risk wards is critical for treatment and infection control.