Emergence of a novel conjugative hybrid virulence multidrug-resistant plasmid in extensively drug-resistant Klebsiella pneumoniae ST15.

INTRODUCTION

Co-existence of both virulence and multidrug-resistant (MDR) determinants on a self-transmissible plasmid facilitates simultaneous transfer of virulence and resistance in a single event and rapid emergence of virulent and MDR Klebsiella pneumoniae clones.

METHOD

This study identified extensively drug-resistant ST15 strains, KP17-15 and KP17-16, from clinical cases with microbiological and genomical approaches.

RESULTS

The chromosomes of KP17-15 and KP17-16 were highly homologous with 12 SNP differences, indicating that the two strains were derived from the same clone. Multiple plasmids existed in the isolates, including novel virulence plasmids p17-15-vir (479 kb) and p17-16-vir (290 kb) for KP17-15 and KP17-16, respectively. Notably, the plasmid p17-15-vir (479 kb) was a hybrid plasmid that might be formed by recombination of two homologous regions encoding group II intron reverse transcriptase and mobile element ISShes11 shared by p17-16-vir (290 kb) and a conjugative MDR plasmid p17-16-CTX (188 kb). p17-15-vir was readily transferable to ST11 Klebsiella pneumoniae by conjugation. Moreover, p17-16-vir, a non-conjugative virulence plasmid lacking the transfer (tra) operon, was also transferable by conjugation under the help of p17-16-CTX or p17-16-KPC. Fusion of p17-16-vir with p17-16-CTX into a p17-15-vir-like plasmid was also observed in the transconjugant.

CONCLUSION

The findings uncover the evolutionary pathway of a novel hybrid virulence MDR plasmid and transfer mechanism of a non-conjugative virulence plasmid. Systematic surveillance of such hybrid virulence MDR plasmids in clinical Klebsiella pneumoniae should be performed.