Resistance of strains producing extended-spectrum beta-lactamases and genotype distribution in China

To investigate the resistance of Escherichia coli and Klebsiella pneumoniae producing extended-spectrum beta-lactamases (ESBLs) and the genotyping of ESBLs in China.

MICs of 12 antibiotics against 50 strains (by random selection) of ESBLs-producing E. coli and K. pneumoniae were determined by E-test. The genotypes of ESBLs were analyzed by PCR, DNA sequencing and isoelectric focusing.

The susceptibility rate of 50 isolates was 100% in imipenem, 60%-80% in cefoperazone/sulbactam, ceftazidime and piperacillin/tazobactam, and lower in other antimicrobial agents tested. Only 6.0% of the isolates were sensitive to cefotaxime. Four hundred and forty-seven of 509 isolates had been confirmed the genotype of ESBLs. Four hundred and sixteen strains produced only one type of ESBLs, including CTX-M-14 (271 strains), CTX-M-3 (70 strains), CTX-M-24 (35 strains), CTX-M-22 (8 strains), CTX-M-15 (4 strains), CTX-M-9 (4 strains), CTX-M-28 (3 strains), CTX-M-12 (1 strain), CTX-M-13 (1 strain), CTX-M-27 (1 strain), CTX-M-29 (1 strain), SHV-12 (10 strains), SHV-5 (4 strains), SHV-2 (2 strains), and SHV-9 (1 strain). Thirty isolates carried two or three types of ESBLs, and producing CTX-M-14 and CTX-M-3 together were the most common type.

The resistance of E. coli and K. pneumonia producing ESBLs in China was a serious issue and CTX-M type ESBLs were the most common genotype. CTX-M-14 was the predominant genotype. Some isolates produced two or three ESBLs.