临床分离大肠埃希菌和克雷伯菌质粒介导AmpCβ内酰胺酶的研究

Prevalence of plasmid-mediated AmpC beta-lactamases in Escherichia coli and Klebsieila spp. isolated in children

目的 研究儿科临床大肠埃希菌和克雷伯菌中质粒介导AmpC β内酰胺酶的检出率和基因型.方法 收集2009年1至12月北京儿童医院住院患儿中分离的大肠埃希菌和克雷伯菌.采用头孢西丁纸片扩散法进行大肠埃希菌和克雷伯菌AmpC酶表型初筛,对AmpC酶表型阳性大肠埃希菌和克雷伯菌用多重聚合酶链反应（PCR）方法测定质粒AmpC酶MOX、CIT、DHA、ACC、MIR及FOX基因型.结果 大肠埃希菌和克雷伯菌中,共筛选出65株对头孢西丁不敏感的菌株,经多重PCR扩增,有17株AmpC酶DHA型基因阳性,DHA型质粒AmpC酶的总检出率为26.2%.其中,肺炎克雷伯菌14株DHA-1基因阳性,检出率为38.9%（14/36）;大肠埃希菌2株DHA-1基因阳性,检出率为7.7%（2/26）;产酸克雷伯菌1株DHA-1基因阳性,检出率为33.3%（1/3）.其余48株质粒AmpC酶MOX、CIT、DHA、ACC、MIR及FOX型基因均为阴性.结论 儿科临床分离的大肠埃希菌和克雷伯菌中,均有质粒介导DHA-1型AmpC酶的产生,其中肺炎克雷伯菌的产生率更高.

Objective To study the plasmid-mediated AmpC β-lactamases and the genotypes of Escherichia coli and Klebsieila spp. in children. Methods Escherichia coli and Klebsieila spp. of strains were isolated at our division from January to December 2009. Cefoxitin disk diffusion method was used to screen Escherichia coli and Klebsieila spp. for phenotypic AmpC enzyme. Multiple PCR method was adopted to test the genotypes of AmpC enzyme-positive Escherichia coli and Klebsieila spp. strains. Results Of all Escherichia coli and Klebsieila spp. , 65 were insensitive to cefoxitin disk and 17 strains carried DHA type AmpC gene. The prevalence of plasmid-mediated AmpC enzyme in Escherichia coli and Klebsieila spp. was 26. 2% （17/65）. Among plasmid-mediated AmpC enzyme isolates, 14 （38.9%） Klebsiella pneurnoniae strains, 2 （7.7%） Escherichia coli strains and 1 （33.3%） Klebsiella oxytoca strains carried the DHA-1 AmpC gene. The genes of MOX, CIT, DHA, ACC, MIR and FOX were not found in other 48 strains. Conclusions The identified plasmid-mediated AmpC genes are all of DHA-1 genotype in Escherichia coli and Klebsieila spp. The prevalence of plasmid-mediated AmpC enzyme in Klebsiella pneumoniae isolates is relatively high in children.