产质粒介导Ⅰ型头孢菌素酶细菌的耐药性及基因型研究

Study of susceptibility and genotype characterization of plasmid-med iated classⅠ cephalosporinase in gram-negative bacteria

目的 了解华南地区产 β内酰胺酶中质粒介导的Ⅰ型头孢菌素 (AmpC)酶细菌的耐药性及其基因型特征。方法 收集革兰阴性菌临床分离无重复菌株共 1187株 ,采用头孢西丁三维试验检测AmpC酶 ,Kirby Bauer琼脂扩散法检测耐药性 ;质粒结合试验 ,聚合酶链反应 (PCR)通用引物扩增各组基因及测序以确定AmpC酶基因型。结果 革兰阴性菌头孢西丁三维试验阳性率为 5 9%(70 /1187) ,其中质粒介导的AmpCβ内酰胺酶的检出率为大肠杆菌 4 2 % (19/451) ,克雷伯菌属 4 7%(16/3 3 9) ,肠杆菌属 2 1% (4/190 ) ,产碱杆菌属 5 3 % (1/19) ,不动杆菌属 2 2 % (1/45) ,总检出率为3 5% (41/1187)。药敏显示结合子对头霉素和氨苄西林耐药 ,对头孢吡肟和亚胺培南敏感。PCR扩增和测序结果证实为blaDHA 1基因和blaACT 1基因 ,主要分布于克雷伯菌属和大肠杆菌属。结论华南地区质粒介导AmpC酶的基因型以DHA 1和ACT 1为主。

ObjectiveTo investigate the susceptibility and genotype characteristics of gram-negative bacteria producing plasmid-mediated classⅠ cephalosporinase (AmpC β lactamase) epidemic in Southern China. Methods A total of 1 187 clinical isolates of nonrepetive gram-negative bacteria were collected from different cities in Southern China. AmpC β lactamase producing isolates were identified by cefoxitin three-dimensional test, and antimicrobial susceptibility test was identified by Kirby-Bauer agar diffusion test;plasmid conjugation,plasmid extraction,universal PCR for gene amplication of corresponding group was done,and the PCR products were sequenced subsequently. Results The positive rate of cefoxitin three-dimensional test in gram-negative bacteria was 5.9%(70/1 187),and the prevalence of plasmid-mediated AmpC β lactamase was:E.coli:4.2%(19/451),Klebsiella: 4.7%(16/339),Enterobacter: 2.1%(4/190),Alcaligenes: 5.3%(1/19),Acinetobacter: 2.2% (1/45) and the total posit ive rate was:3.5% (41/1 187). The susceptibility test showed that compared with the clinical isolates,the transconjugations remained resistance to cephamycins and ampicillin,and susceptible to cefepime and imipenem. PCR amplication and sequencing confirmed them to be bla DHA-1 gene and bla ACT-1 gene,and they were mainly distributed in Klebsiella and Escherichia. Conclusions DHA-1 and ACT-1 were the most common genotypes in plasmid-mediated AmpC β-lactamase produced by clinical isolates in Southern China. Fourth-generation cephalosporins and carbapenems could be better choices for the treatment of infection caused by AmpC βlactamase producers.