Molecular characterization of clinical multidrug-resistant Klebsiella pneumoniae isolates

Background: Klebsiella pneumoniae is a frequent nosocomial pathogen, with the multidrug-resistant (MDR) K. pneumoniae being a major public health concern, frequently causing difficult-to-treat infections worldwide. The aim of this study was to investigate the molecular characterization of clinical MDR Klebsiella pneumoniae isolates. Methods: A total of 27 non-duplicate MDR K. pneumoniae isolates with a CTX-CIP-AK resistance pattern were investigated for the prevalence of antimicrobial resistance genes including extended spectrum beta-lactamase genes (ESBLs), plasmid-mediated quinolone resistance (PMQR) genes, 16S rRNA methylase (16S-RMTase) genes, and integrons by polymerase chain reaction (PCR) amplification and DNA sequencing. Plasmid replicons were typed by PCR-based replicon typing (PBRT). Multi-locus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) were carried out to characterize the strain relatedness. Results: All the isolates co-harbored 3 or more resistance determinants. OqxAB, CTX-M-type ESBLs and RmtB were the most frequent determinants, distributed among19 (70.4%), 18 (66.7%) and 8 (29.6%) strains. Fourteen isolates harbored class 1 integrons, with orfD-aacA4 being the most frequent gene cassette array. Class 3 integrons were less frequently identified and contained the gene cassette array of bla(GES-1)- bla(OXA-10)-aac(6')-Ib. IncFII replicon was most commonly found in this collection. One cluster was observed with >= 80% similarity among profiles obtained by PFGE, and one sequence type (ST) by MLST, namely ST11, was observed in the cluster. Conclusion: K. pneumoniae carbapenemase (KPC)-producing ST11 was the main clone detected. Of particular concern was the high prevalence of multiple resistance determinants, classs I integrons and IncFII plasmid replicon among these MDR strains, which provide advantages for the rapid development of MDR strains.