Prevalence of extended-spectrum β-lactamases in isolates of the Enterobacter cloacae complex from German hospitals

ABSTRACTIn 2002, 119 isolates of the Enterobacter cloacae complex were collected randomly from 11 German laboratories nationwide. Antibiotic susceptibilities were tested by disk-diffusion tests according to CLSI guidelines, and MICs were determined using Etests. PCRs were performed to amplify all TEM and SHV, and most CTXM and OXA β-lactamase genes. PCR products were sequenced to identify the precise extended spectrum β-lactamase (ESBL) types. Isoelectric focusing (IEF) and PM/PML Etests were used to confirm production of the respective ESBLs. According to susceptibility tests and CLSI criteria, 49 (40%) isolates were resistant to extended-spectrum cephalosporins. Seven (5.8%) isolates were positive in at least one of the PCR assays. Sequencing identified production of TEM-1 β-lactamase genes by three (2.9%) isolates, and ESBL genes of the CTXM and SHV β-lactamase families by five (4.2%) isolates. IEF confirmed the production of β-lactamases in the expected pI ranges of the respective ESBLs, and four of the five ESBL-producers were detected using the PM/PML Etest. All ESBL-producing isolates showed co-resistance to sulphonamides.