Relationship Between AcrAB-Tolc And KPC-2 Producing Klebsiella Pneumoniae In Tigecycline Resistance Mechanism

Objective:To investigate relationship between Acr AB-Tol C and KPC-2 Producing Klebs-iella pneumoniae in tigecycline resistance mechanism.Methods:KPC-2 Producing Klebsiella pneumoniae strains were collected from January to October,2016.Identification and drug susceptibility of isolates were carried out with VITEK-2 compact system.The minimum inhibitory concentration(MIC)of tigecycline was determined by E-tests.Efflux pump genes(acr A,acr B,tol C)and their regulators(mar A,ram A,sox S)were examined by PCR.Expression levels of them were examined by real-time PCR.Efflux pump inhibitors(EPIs)-carbonyl cyanide chlorophenylhydrazone(CCCP)and reserpine were able to reverse the resistance strains.Molecular typing was performed by multilocus sequence typing(MLST).Results:A total of 18 KPC-2 producing tigecycline-nonsusceptible Klebsiella pneumoniae isolates were collected.All isolates efflux pump genes and regulators were found.Compared with isolate A13,a higher expression level of them.A significant association between acr B and mar A expression and tigecycline MICs was observed.Exposure of isolates to CCCP and reserpine resulted in an obvious decrease in the MICs of tigecycline and acr B and mar A expression levels.All isolates belonged to ST 11.Conclusions:Acr AB-Tol C is prevalent in ST11 in KPC-2 producing tigecycline-nonsusceptible Klebsiella pneumoniae strains.Increased expression of efflux pump gene acr B and pump regulators mar A are main cause of the decrease in the MICs of tigecycline.While,pump genes acr A and tol C and regulator sox S and ram A are not related to tigecycline-resistance Klebsiella pneumoniae.