生物被膜大肠埃希菌AmpC酶、超广谱β-内酰胺酶的检测

Investigation on the AmpC and ESBLs produced in the biofilm of Escherichia coli

目的探讨大肠埃希菌生物被膜(biofilm,BF)的耐药情况,为临床合理应用抗生素提供理论依据。方法应用改进的平板培养法建立大肠埃希菌BF模型,用银染法和扫描电镜观察鉴定。采用改良三维试验法检测超广谱β-内酰胺酶(ESBLs)及AmpC酶。结果浮游大肠埃希菌(A组)单产AmpC,单产ESBLs酶及同时产ESBLs和AmpC酶的菌株分别为5.0%(2/40)、30.0%(12/40)和12.5%(5/40);BF大肠埃希菌(B组)单产AmpC酶,单产ESBLs及同时产ESBLs和AmpC酶的菌株分别为10.0%(4/40)、45.0%(18/40)和22.5%(9/40)。对A组和B组的检出率两两分别进行χ2检验,结果均为P<0.05。产酶有BF大肠埃希菌对10种抗生素(除亚胺培南全部敏感外)的耐药率均较高。结论BF的形成和产生ESBLs及AmpC酶的协同作用是大肠埃希菌耐药的主要原因之一。

Objective To evaluate the resistance mechanism of Escherichia coli growing in biofilm, and to provide the theoretical guide to select antimicrobial agents in clinic. Methods Model of Escherichia coli bacterial biofilm was built up by the modified flat-board method and identified by the method staining with AgNO3 and confocal scanning laser microscopy. ESBLs and AmpC β-lactamase were detected by improved three-dimension test. Results The detection rates of AmpC, ESBLs and ESBLs plus AmpC β-lactamase Escherichia coli were 5.0% （2/40）, 30.0% （12/40） and 12.5% （5/40）, whereas those in biofilm Escherichia coli were 10. 0% （4/40）, 45.0% （18/40） and 22.5% （9/40） respectively, the resistant rate of the biofilm Escherichia coli producing AmpC and ESBLs to 10 kinds of antibiotics was higher （except imipenem）. Conclusion One of the main reasons that Escherichia coli was resistant to antibiotics was the synergetic effect of ESBLs, AmpC and biofilm.