Study on the molecular mechanism of the dissemination of a novel CTX-M-like extended spectrum beta-lactamase-producing Escherichia coil / 中国医师杂志

ABSTRACT

Objective To investigate the distribution of the CTX-M- extended spectrum beta-lactamase (ESBLs) producing Esche- richia coli(ECO) and the molecular mechanism of dissemination. Methods To analyze the drug resistance of the 43 isolates, Kirby-Bauer susceptibility method was used. Multiple polymeraso chain reaction (PCR) was used to amplify the gene of ESBLs, AmpC, full length of blaCTX-M-like gene, insertion sequence (IS) ISEcp1B, IS903 , IS26 and integron I. NEST-PCR was used to detect if the beta-lactamase gene lo- cated in the integron I. The product of full length of bla-CTX-M like gone amplified by PCR was sequenced. Results Susceptibility test showed the resistance from high to low in turn was Ampicillin (97.68%), Coftriaxone (67.44 % ), piperacillin(65.12 % ), Cefotaxime (62.79 % ) ,Coftasidime(58.14% ), Cofasolin(55.81% ), Cofepime (53.49%), Cefexitin(51.16%), ciprofloxacin (44. 19% ), Aztreo- nam(41.86% ), Cefoperasone/Sulbactam ( 20.93% ), Amikacin (0% ), Imipenem (0% ), respectively. ECO was susceptive to Imipenem. CTX-M-G1 was found in 25 strains of ECO , TEM, SHV, CTX-M-G1, ISEcp1B, and integron I were found in the nine isolates. IS903 were found in ECO 3 and 5, and IS26 was found in ECO 3. In ECO 3 and 5, blaCTX-M-like was flanked upstream by ISEcp1B element that provided -35 and -10 promoter sequences and a right inverted repeat (IRR) recognized by transposase, downstream by IS903 provided an inverted re- peat, ISEcp1 B and IS903 composed the complex transpeson. Conclusion ISEcplB may drive the expression and dissemination of blaCTX-M-like gene at a high level.