Mechanisms of Tigecycline Resistance among Klebsiella pneumoniae Clinical Isolates

Abstract

ABSTRACTOf 26 tigecycline-nonsusceptibleKlebsiella pneumoniae (TNSKP) clinical isolates, 25 had nonsynonymous mutations inramRand/oracrR(23 inramRand 10 inacrR). Eight TNSKP isolates possessed overexpression oframA,acrB,rarA, andoqxBsimultaneously, while 8 and 1 TNSKP strains had upregulation oframAandacrBand ofrarAandoqxB, respectively. Thus, resistance mechanisms of 9 TNSKP isolates cannot be explained by the present pathways. This study underscores the role of RamA in TNSKP and suggests the presence of novel tigecycline resistance mechanisms.