High Prevalence of Plasmid-Mediated Quinolone Resistance Determinants Among Serotype K1 Hypervirulent Klebsiella pneumoniae Isolates in China.

Abstract

Thirty-five serotype K1 hypervirulent Klebsiella pneumoniae (K1-hvKP) isolates collected from a Chinese hospital during the whole year of 2017 were evaluated to characterize the prevalence of the plasmid-mediated quinolone resistance (PMQR) genes. In total, 18 (51.4%) isolates were detected to carry PMQR genes, and the most frequently detected gene was qnrS1 (37.5%), followed by aac(6')-Ib-cr (15%) and qnrB4 (2.5%). Remarkably, some qnr-carrying strains had only a single or more quinolone resistance-determining region mutations in GyrA or ParC, and most exhibited high-level ciprofloxacin resistance. However, only 11.4% (4/35) isolates were resistant to quinolones. Furthermore, 34.3% (12/35) carried extended-spectrum β-lactamase (ESBL) genes, but only 14.3% (5/35) exhibited ESBL phenotype. The most prevalent virulence genes were mrkD (100%, 21/21), followed by magA (97.1%, 34/35), wabG (97.1%, 34/35), rmpA (97.1%, 34/35), aerobactin (94.3%, 33/35), kfuB (94.3%, 33/35), ycf (91.4%, 32/35), iutA (91.4%, 32/35), rmpA2 (62.9%, 22/35), wcaG (62.9%, 22/35), ybtS (51.4%, 18/35), allS (45.7%, 16/35), and iroN (22.9%, 8/35). Multilocus sequence typing (MLST) analysis assigned the 35 K1-hvKP isolates into 5 sequence types (STs), with ST23 encompassing 77.1% of the strains. Pulsed field gel electrophoresis (PFGE) typing showed that strains closely related by MLST clustered in major PFGE clusters, of which cluster A accounts for 16 ST23 isolates and cluster B includes 11 ST23 isolates. The analysis of the transconjugants showed decreased susceptibility to quinolones and revealed a cotransfer of blaCTX-M-15 with the qnrS1 alleles. Cumulatively, our findings showed that the PMQR-producing K1-hvKP strain is covertly spreading even when K1-hvKP is rarely resistant to fluoroquinolones (FQs) according to the Clinical and Laboratory Standards Institute criteria. It is therefore critical to continuously monitor the PMQR-producing K1-hvKP epidemiology and minimize potential risks from FQ-resistant K1-hvKP.