Molecular Characterization of Extended-Spectrum β-Lactamases Produced by Clinical Isolates of Enterobacter cloacae from a Teaching Hospital in China

Of 59 clinical isolates of Enterobacter cloacae from a teaching hospital in Sichuan, China, 18 isolates were shown to be resistant to oxyimino cephalosporins and aztreonam. Enterobacterial repetitive consensus PCR revealed that these isolates comprised 7 distinct genotypes. The presence of plasmids in the 18 clinical isolates was revealed by conjugational transfer of plasmids from E. cloacae to Escherichia coli with the further isolation of the plasmids in the transconjugants. Subsequent nucleotide sequencing and β-lactamase isoelectric focusing indicated that the plasmids encoded blaSHV, blaCTX-M and/or blaTEM genes, including genes for CTX-M-22 (13 strains), TEM-1 (12 strains), TEM-29 (1 strain), TEM-141 (1 strain), TEM-157 (1 strain), SHV-5 (1 strain), SHV-12 (1 strain), and SHV-70 (1 strain). The widespread presence of extended-spectrum β-lactamases in E. cloacae isolated from the southwest of China was likely due to the dissemination of resistance plasmids with the predominant genotype of blaCTX-M-22.