Resumo

Introduction: Multi-drug resistant gram negative bacilli is a worldwide problem, especially high-risk international clones carrying epidemic/transmissible plasmids harboring beta-lactamase-encoding genes. The aim of this study was to investigate the genetic determinants of antimicrobial resistance and virulence factors in the polymyxin B-resistant KPC-2-producing Klebsiella pneumoniae ST11 clone (RP29, RP59 and RP62 bacteria) isolated in January 2012, in the Clinical Hospital of the Faculty of Medicine of Ribeirao Preto-USP (HCFMRP-USP), Brazil. Materials and Methods: The investigation of determinants of resistance included typing of blaKPC-2 genetic environmental (PCR, RFLP and sequencing), conjugation experiment in order to transfer blaKPC-2 (liquid-medium mating) and plasmid analysis (PCR-Based Replicon Typing [PBRT], MLST and hybridization of S1-PFGE product). For virulence factors, PCR assays were performed to search ten virulence encoding genes (ureA, fimH, kfuBC, uge, wabG, magA, mrkD, allS, rmpA and cf29a) that have been associated with virulence phenotype in K. pneumoniae. In addition, the K. pneumoniae phylogenetic group was evaluated. Results and Discussion: blaKPC-2 was located on transposon Tn4401 variant "a". This genetic context was harbored on ~100kb-IncFIIk plasmid. Besides, the RP29 bacteria harbored other three plasmids (~510, 450 and 388kb) and RP59 and RP62 harbored another plasmid (~388kb) that were untypeable by PBRT scheme. The blaKPC-2 resistant gene was transferred, rending transconjugants bacteria resistant to all (and only) beta-lactam antimicrobials. Five of virulence encoding genes were detected (ureA, fimH, uge, wabG and mrkD). mrkD gene, for example, coding for the type 3 fimbriae adhesin, which facilitates adhesion to the basement membranes of several human tissues. Hypermucoviscous phenotype, related to virulence and resistance to polymyxin, was detected in the RP59 bacteria. Determinants of resistance to polymyxin B are being investigate. In addition, the KpI K. pneumoniae phylogenetic group was determined. Conclusions: Important genetic determinants of resistance and virulence were detected in polymyxin B-resistant KPC-2-producing K. pneumoniae ST11 clone facilitating infections and the dissemination in the HCFMRP-USP as well as to other centre. This clone can be selected and it becomes prevalent and pan-drug resistant.