The Effects Of Biofilm On The Expression Of AdeABC Efflux Gene And Oxacillinase In Imipenem Resistant Acinetobacter Baumarmii

Objective1.In order to further explore the imipenem-resistant mechanism in clinical Acinetobacter baumannii(AB)isolates,the epidemiological characteristics and correlation of OXA,Ade ABC,CarO genes and biofilm-producing isolates between clinical imipenem-resistant and imipenemsensitive strains were investigated by analyzing distributions of these genes and biofilm formation in clinical AB isolates.2.In order to better understand the mechanism of biofilm formation in the drug-resistance of Acinetobacter baumannii(AB),the impact of biofilm on the expression of oxacillinase(OXA)and Ade ABC efflux pump genes in clinical oxacillin–resistant isolates was examined.Methods1.Biofilms of 106 clinical AB isolates were established and quantified in terms of a microtiter plate assay;the presence of OXA-23,24,51,58 and AdeABC efflux pump genes were detected using a multiple PCR method;the mRNA expression of OXA-23 and Ade B genes in 35 biofilm-producing AB clinical isolates was analyzed by a quantitative real-time RT-PCR(qRT-PCR);an E-test was used for accessing the minimum inhibitory concentration(MIC)bacteria to imipenem.2.106 imipenem-resistant and 102 imipenem-sensitive clinical AB strains were isolated from the General Hospital of Ningxia Medical University.The drug-resistant genes were detected with PCR technology,biofilm formation and quantitative experiment were carried out with microtiter plate methodResults1.our results showed that the OXA-23 gene was expressed in 99.1% and 2.9% imipenemresistant and imipenem-sensitive strains,respectively(P<0.05);The OXA-51 gene was detected in all tested clinical isolates,while the OXA-58 gene was not detected in all examined strains;OXA-24 was found in one imipenem-resistant isolate.The distribution of AdeABC efflux pump genes showed a significant variation between isolates,the Ade A,Ade B and Ade C genes were detected in almost imipenem-resistant strains(98.1%)and the rate of all the three genes expressed simultaneously in these isolates was 98.1%.In addition,the rate of imipenem-sensitive strains where AdeA、Ade B and Ade C were expressed was 64.7%,82.4% and 66.7% respectively.The rate of imipenem-sensitive strains where three genes above were expressed simultaneously was 64.7%.The rate of imipenem-resistant or imipenem-sensitive strains where CarO gene was expressed was 97.2% or 99.0%,respectively.The rate of imipenem-resistant or imipenem-sensitive strains which can produce bifilm was 67.9% or 75.5%,respectively.2.The rate of biofilm-producing or no biofilm-producing of 106 imipenem-resistant strains was 67.9% or 32.1%.The mRNA level of OXA-23 and Ade B were significantly more than that in Broth culture and suspension condition.MIC in biofilm-producing strains was higher that that in no biofilm-producing strains.Conclusion1.Besides OXA-51 expressed in all of imipenem-resistant and imipenem-sensitive strains,OXA-23,the second popular gene,was the major OXA subtype of imipenem-resistant in this hospital,which hints that OXA-23 play important roles in Penicillium carbon alkene antibiotic resistance mechanisms of Acinetobacter baumannii.The distribution of AdeABC gene between imipenem-resistant and imipenem-sensitive strains was difference,which suggest that AdeABC plays indispensable roles in increasing the drug resistance of Acinetobacter baumannii.Caro gene was expressed in almost strains,which infer that Caro may not work i n regulating the imipenem-sensitivity of Acinetobacter baumannii.The infection caused by clinical Acinetobacter baumannii was related to biofilm formation.2.The biofim formation of Acinetobacter baumannii can promote OXA-23 and Ade ABC efflux pump gene expression,which enhanced imipenem-resistance of Acinetobacter baumannii.