The Study Of TEM-derived Extended-expectrum β-lactamases In E. Coli And K. Pneumoniae Resistant To Ceftazidime

【Objective】To detect TEM-derived extended-expectrumβ-lactamases (ESBLs) inE. coli and K. pneumoniae of 19 hospitals in China.【Method】Ninety-eight E. coli and one hundred and nine K. pneumoniae resistantto ceftazidime were collected from 2004 to 2005 in 19 hospitals in China. Theirantimicrobial susceptibilities and ESBL-producing percentage were detected by 2-foldagar diffusion method. Their bla_TEM genes were amplified by PCR. The conjugationtest were used to detect the location and transmission of ceftazidime resistance gene,and all the conjugants' MICs were also determined, followed by PCR amplification.The isoelectric points (pIs) of theβ-lactamases were determined by Isoelectricfocusing analysis (IEF). Denaturing high-performance liquid chromatography(DHPLC) and DNA sequencing were used to detected the point-mutation. Thencollected all the swains isolated from the host whose strains expressing TEM-derivedESBLs and the strains non-susceptible to ceftazidime isolated from the same ward,analyzed them by antimicrobial susceptibility testing, bla_TEM gene PCR amplified,DHPLC and DNA sequenceing, and typed by Enterobacterial Repetitve IntergenicConsensus sequence PCR (ERIC-PCR) and Randomly Amplified Polymorphic DNA(RAPD) analysis.【Results】For the 98 E. coli and 109 K. pneumoniae resistant to ceftazidime,imipenem was the most suscepitible antimicrobial agent (100% and 99.1% susceptible,respectively), cefotaxime was the least suscepitible one (8.2% and 12.8% susceptible,respectively). There were 84.7% E. coli and 68.8% K. pneumoniae producing ESBLs,67.3% E. coli and 69.7% K. pneumoniae expressed bla_TEM, and 63.6% E. coli and77.6% K. pneumoniae successfully conjugated. IEF showed that only 4 E. coli andtheir conjugants showed another band except pI=5.4 in the zone of pIs of TEMβ-lactamases (pH 5.2～6.5). Only 1 E. coli (No. P34) expressing TEM-12 was detectedby DHPLC and DNA sequenceing, all the others expressed TEM-1. In the 21 E. coliisolated from the host of P34, there were 18 strains expressed TEM-12, and all the 21strains belonged to the same clone. All the 11 E. coli non-susceptible to ceftazidime isolated from the same ward with P34 expressed TEM-1, and belonged to differentclones with P34. But there were still clone-spreading between different patients there.【Conclusions】TEM-derived ESBLs were still rare in China, and they were not themain factors for the resistance to ceftazidime of E. coli and K. pneumoniae. This is thefirst report of the E. coli expressing TEM-12 in China. The infection control meansshould be enhanced to provent the spread of TEM-derived ESBLs in China.