不同底物应用于CIM法检测鲍曼不动杆菌的可行性

The feasibility of using different substrates for the determination of Acinetobacter baumannii by CIM method

目的评价美罗培南(MPN)、亚胺培南(IPN)和厄他培南(ETP)3种不同药敏纸片作为底物应用于碳青霉烯酶表型检测法(CIM)检测产碳青霉烯酶的鲍曼不动杆菌的可行性。方法选择邢台市第三医院2015年1-12月和河北医科大学第二医院2015年5-6月从临床标本分离所得的非重复鲍曼不动杆菌88株,经LB培养基复苏,在血培养基35℃,5%CO2过夜培养后,准备A、B、C三组EP管,用10μL接种环挑取满环细菌分别加入A、B、C 3管中,混匀后再分别加入10μg美洛培南、亚胺培南、厄他培南药敏片,检测鲍曼不动杆菌的碳青霉烯酶,并以经典PCR方法检测耐药基因OXA-23为金标准,比较3种药敏片作为底物的CIM法检测产OXA-23型碳青霉烯酶的鲍曼不动杆菌的效果。结果 88株鲍曼不动杆菌有57株显示OXA-23基因阳性,IMP、VIM、KPC、OXA-48基因均为阴性。57株OXA-23基因阳性的菌株中美罗培南、亚胺培南、厄他培南的检出率分别为93.0%(53/57)、77.2%(44/57)、73.7%(42/57),亚胺培南和厄他培南阴性菌株经过加入3倍菌量再次实验,检出率分别为89.5%(51/57)和87.7%(50/57)。31株OXA-23基因阴性的菌株中,美罗培南CIM试验2株阳性,亚胺培南和厄他培南检测均有1株阳性。3种药敏片的CIM试验和金标准OXA-23基因比较,差异无统计学意义(P>0.05)。结论应用美罗培南、亚胺培南和厄他培南为底物的CIM法检测产OXA-23型碳青霉烯酶的鲍曼不动杆菌都是很好的检测方法,但是亚胺培南和厄他培南需要加大3倍菌量。

Objective To evaluate of three different drug susceptibility disks,meropenem（MPN）,imipenem（IPN）and ertapenem（ETP）as substrates for the determination of carbapenemase-producing Acinetobacter baumannii by carbapenem inactivation method（CIM）.Methods Clinical specimens were collected from patients with nosocomial infection in the Third Hospital of Xingtai City since January 2015 to December and the Second Affiliated Hospital of Hebei Medical University since May 2015 to June.A total of 88 strains of Acinetobacter baumannii were isolated and recovered by LB medium.The strains were then cultured on blood culture medium at 35℃,5% CO2 for overnight.Each strain cuolture was then inoculated into A,B and C EP tubes using a 10 μL inoculation loop.10 μg of MPN,IPN and ETP were added to the A,B and C tubes,respectively,to detect the carbapenase produced by Acinetobacter baumannii.The drug-resistant gene OXA-23 was detected by PCR as the gold standard.The results of the CIM method for the detection of OXA-23 carbapenase using three different substrates were compared.Results 57 of 88 strains showed carrying OXA-23 gene.No IMP,VIM,KPC and OXA-48 genes were detected.The detectable rates of carbapenemase genes by using MPN,IPN,ETP were 93.0%（53/57）,77.2%（44/57） and 73.7%（42/57）,respectively.Repeated experiments with increasing three times of inoculums in IPN and ETP drug slips showed the detectable rates of carbapenemase genes were 89.5%（51/57）and 87.7%（50/57）.Among 31 strains of OXA-23 negative,2 were detected positive by MPN CIM test,and 1 was detected positive by IPN and ETP CIM test.There was no significant difference between CIM test using MPN,IPN or ETP,and OXA-23 gene gold standard test（P〉0.05）.Conclusion The CIM（MPN）,CIM（IPN）and CIM（ETP）could rapidly detect carbapenemase producing in Acinetobacter baumannii,but CIM（IPN）and CIM（ETP）needed three folds of inoculums of bacteria isolates.