不同底物在CIM试验检测革兰阴性杆菌碳青霉烯酶中的应用评价

Methodological appraisal of different substrates of carbapenem inactivation method in carbapenemase detection of gram-negative bacillus

目的评价不同碳青霉烯类抗生素作为指示底物对碳青霉烯类抗生素不活跃检测方法(CIM)结果的影响。方法分别用美罗培南、亚胺培南和厄他培南作为指示药物,对90株肠杆菌科细菌和105株非发酵菌进行CIM试验来检测碳青霉烯酶,并用PCR方法检测碳青霉烯酶基因。结果肠杆菌科细菌中碳青霉烯酶基因阳性菌株用美罗培南检出率为91.0%(71/78),亚胺培南检出率为92.3%(72/78),厄他培南检出率为85.9%(67/78),3种药物检出率差异无统计学意义(χ2=1.95,P=0.377);肠杆菌科细菌中碳青霉烯酶基因阴性菌株CIM试验用美罗培南、亚胺培南和厄他培南检测均阴性。非发酵菌碳青霉烯酶基因阳性菌株用美罗培南检出率为94.0%(63/67),亚胺培南检出率为74.6%(50/67),厄他培南检出率为70.1%(47/67),美罗培南检出率均高于厄他培南和亚胺培南的检出率,差异有统计学意义(P<0.05)。32株碳青霉烯酶基因阴性鲍曼不动杆菌菌株中有2株美罗培南CIM试验阳性,而亚胺培南和厄他培南检测均阴性。结论应用美罗培南作为反应底物进行CIM试验与基因检测的一致性最高。此方法操作简单,成本低廉,结果易判断,适合在临床实验室开展。

Objective To evaluate the effects of different carbapenem as the substrate indicators on the results of the carbapenem inactivation method （CIM） for gram-negative bacillustest. Methods Carbapenemase in 90 strains of Enterobacteriaceae and 105 strains of nonfermenters was detected by CIM test in which meropenem, imipenem, ertapenem were used as substrates. Carbapenemase genes were detected by PCR method. Results The detectable rates of carbapenemase genes by using meropenem, imipenem, ertapenem were 91.0% （71/78）, 92.3 % （72/78） and 85.9% （67/78）, respectively in all the enterobacteriaceae strains with positive carbapenemase genes, and the differences were not statistically significant （χ2 = 1.95,P = 0. 377）. The results of CIM test for the enterobacteriaceae strains with negative carbapenemase genes were all nagetive by using the three carbapenem antibiotics. The detectable rates of CIM in nonfermenters with positive carbapenemase genes were 94.0% （63/67）, 74.6% （50/67）, 70.1% （47/67） by using meropenem, imipenem and ertapenem, respectively. The detectable rate of CIM by using meropenem was significantly higher than that of imipenem and ertapenem （ P 〈 0.05 ）. The results of CIM test were positive in two of 32 Acinetobacter baumannii with negative carbapenemase genes detected by meropenem disk, but they were nagative detected by imipenem and ertapenem disk. Conclusion CIM test by using meropenem as substrates showed the highest consistency with the results of carbapenemase gene detection. The method should have high specificity, sensitivity The operation of the method was easy and cost-saving, so it should be suitable for application in clinical laboratories.