肺炎克雷伯菌和产酸克雷伯菌中ESBLs和AmpC酶基因的研究

Genes of Extended Spectrum β-Lactamases and AmpC β-Lactamase from Klebsiella pneumoniae and Klebsiella oxytoca

目的研究肺炎克雷伯菌、产酸克雷伯菌中ESBLs和AmpCβ-内酰胺酶的存在形式及其基因类型和转移方式。方法利用CLSI纸片法确认实验和APB纸片增强试验分别检测ESBLs和AmpC酶,基因芯片技术和序列分析测定两种酶基因的类型,接合转移实验了解肺炎克雷伯菌和产酸克雷伯菌耐药基因转移方式。结果在对头孢西丁不敏感的72株肺炎克雷伯菌和20株产酸克雷伯菌中,以同时产生ESBLs和AmpC酶为主要形式,分别占54.2%和75.0%;单产ESBLs分别为22.2%和25.0%,肺炎克雷伯菌中单产AmpC酶占12.5%;肺炎克雷伯菌和产酸克雷伯菌中的AmpC酶基因绝大多数为DHA型(测得DHA-1型基因),ESBLs则以SHV型为主(测得SHV-12型),它们均能通过接合转移方式将其质粒携带的耐药性传递至受体菌。结论同时存在的ESBLs和AmpC酶是肺炎克雷伯菌和产酸克雷伯菌耐药的主要原因,耐药基因的转移可导致耐药性的传播扩散。

OBJECTIVE To study the phenotypic existence, genetic type and gene transfer of extended spectrum beta-lactamases （ESBLs） and AmpC beta-lactamase from Klebsiella pneumoniae and K. oxytoca. METHODS Disk confirmation test and 3-aminophenylboronic acid （APB） disk potentiation test were used to detect ESBLs and AmpC beta-lactamase. The genetic types of these two kinds of beta-lactamases were examined by gene chip technology and sequence analysis. The transfer of resistance genes was conducted by conjugation. RESULTS From 72 strains of K. pneumoniae and 20 strains of K. oxytoca which were not susceptible to cefoxitin, coexistence of AmpC beta-lactamase with ESBLs together was very common, accounted for 54.2% and 75.0%, single ESBLs accounted for 22.2% and 25.0%,respectively. There were 12.5% single AmpC in K, pneumoniae. DHA type ampC gene and SHV type ESBLs gene were the main molecular types. These genes could be transferred from clinical isolates to recipient E. coli J53. CONCLUSIONS ESBLs as well as AmpC beta-laetamase are the most important resistance mechanism in K. pneumoniae and K. oxytoca. The resistance could be transferred through the bacterial conjugation.