碳青霉烯类耐药阴沟肠杆菌耐药机制研究

Study on the resistance mechanisms of carbapenem-resistant Enterobacter cloacae

目的研究碳青霉烯类耐药阴沟肠杆菌的耐药机制。方法收集福建医科大学附属协和医院2011年8月-2012年8月的碳青霉烯类耐药阴沟肠杆菌,采用琼脂稀释法进行药敏试验;改良Hodge试验筛查菌株是否产碳青霉烯酶;利用PCR扩增碳青霉烯酶基因(KPC、IMP、VIM、NDM)及其他β内酰胺酶基因(SHV、TEM、CTX-M-1组、CTX-M-2组、CTX-M-9组);利用肠杆菌基因重复一致序列分析(ERIC-PCR)进行菌株同源性分析;通过接合试验验证碳青霉烯酶基因是否能水平转移。结果共收集29株阴沟肠杆菌,药敏结果显示对检测抗菌药物耐药率>90%的有3种,分别为头孢他啶(93.1%)、头孢西丁(100%)和氨曲南(93.1%);多黏菌素B耐药率最低为3.4%。改良Hodge试验阳性率为79.3%(23/29)。29株实验菌共检出23株含有β内酰胺酶基因,其中IMP基因阳性17株、KPC基因阳性1株。29株阴沟肠杆菌可分为23个不同的型别,其中1株未能分型。接合试验成功率48.3%(14/29)。结论该院碳青霉烯类耐药阴沟肠杆菌携带碳青霉烯酶基因,以IMP基因较常见。

Objective To investigate the antibiotic resistance mechanisms of carbapenem-resistant Enterobacter cloacae. Methods The modified Hodge test was used for detection of carbapenemase production. The minimum inhibitory concentrations （MICs） were determined using agar dilution method. Carbapenem-resistant genes （KPC, IMP, VIM, NDM） and other β-lactamase genes （SHV, TEM, CTX-M-1 group, CTX-M-2 group and CTX-M-9 group） were analyzed by PCR and sequencing. Enterobacterial repetitive intergenic consensus-polymerase chain reaction （ERIC-PCR） was used to evaluate the genetic similarity between the isolates. A conjugation experiment was performed using broth mating technique. Results A total of 29 isolates were included in this study. Antimicrobial susceptibility testing showed that more than 90% of the strains were resistant to ceftazidime, cefoxitin and aztreonam. The modified Hodge test was positive for 79.3% （23/29） of the isolates. PCR demonstrated a high prevalence （62.1%, 18/29） of carbapenemases in Enterobacter cloacae. IMP-4, IMP-8, and KPC-2 were identified in 11 （37.9%）, 6 （20.7%）, 1 （3.4%） isolates, respectively. Overall, 28 of the 29 isolates belonged to 23 different types. The remaining one strain was nontypeable. Conjugationexperiment was successful for 48.3% （14/29） of the isolates. Conclusions IMPs are the dominant genotypes in the carbapenem-resistant Enterobacter cloacae in our hospital.