产气肠杆菌连续分离株的耐药性及β-内酰胺类抗生素耐药机制的研究

Drug-resistance on consecutive clinical isolates of Enterobacter aerogenes and its resistance mechanism to β-lactamses

目的探讨临床连续分离的产气肠杆菌耐药性及耐碳青霉烯类药物菌株对β-内酰胺类药物耐药的主要机制。方法用Vitek2-Compact仪对临床连续分离的240株产气肠杆菌进行鉴定和常规药敏试验,并筛选出耐碳青霉烯类药物的菌株;用琼脂稀释法测定其对碳青霉烯类药物的MIC值;用改良的三维试验方法分别检测耐药菌株的ESBLs与AmpC酶;改良Hodge试验法检测碳青霉烯酶;用PCR扩增法检测3种β-内酰胺酶的耐药基因;结果 240株产气肠杆菌对23种常用抗生素的耐药率在3.8%-100%之间,最高为头孢西丁（100%）、最低为亚胺培南（3.8%）;筛选出10株耐碳青霉烯类产气肠杆菌;三维试验10株菌ESBLs及AmpC酶均为阳性,Hodge试验阳性7株。PCR结果示,携带blaKPC基因7株;携带blaCTXM基因7株,携带blaSHV基因2株;携带blaDHA基因6株,携带blaACT/MIR型ampC基因4株;16SrRNA基因定量确定ampC基因的表达增加的3株。结论产气肠杆菌对临床常用抗菌药物具有较高的耐药性,其主要耐药机制为产碳青霉烯酶、ESBLs与AmpC酶。

The aim is to investigate the antibiotics resistance of consecutive clinical isolates of Enterobacter aerogens and the main resistance mechanism toβ-lactamses for carbapenems resistant isolates.The Vitek 2-Compact instrument was used to identify the 240 strains of Enterobacter aerogens from clinic,and the antimicrobial susceptibility was tested,while the carbapenems-resistant isolates were screened.The minimum inhibition concentration of carbapenems was tested by standard agar dilution method.The ESBLs and AmpCβ-lactamase were detected with three-dimensional test.The KPC carbapenemase were detected by Hodge test and the genotypes ofβ-lactamses were performed by PCR method.Results showed that the resistance rates of 240 Enterobacter aerogens strains to the common antibiotics were from 3.8%to 100%.The highest one was cefoxitin（100%）,and the lowest was imipenem（3.8%）.Ten carbapenems-resistant strains of Enterobacter aerogens were screened from 240 isolates.Both ESBLs and AmpCβ-lactamase were positive in all of 10 isolates,and 7isolates in Hodge test were positive.PCR experiment showed that among the 10 strains,there were 7strains carrying blaKPC,7strains carrying blaCTX-M,2strains carrying blaSHV,6strains carrying blaDHA,4strains carrying blaACT/MIR,and 2strains carrying high expression levels of the chromosomal ampCgene.It＇s suggested that there is high antibiotic resistance to common antimicrobial agents of clinical Enterobacter aerogens.The main cause for antibiotics resistance of Enterobacter aerogens is producingβ-lactamase such as carbapenemase,ESBLs and AmpC bate-lactamase.