Abstract
International high-risk clones of Klebsiella pneumoniae are among the most common nosocomial pathogens. Increased diversity of plasmid-encoded antimicrobial resistance genes facilitates spread of these clones causing significant therapeutic difficulties. The purpose of our study was to investigate fluoroquinolone resistance in extended-spectrum beta-lactamase (ESBL)-producing strains, including four K. pneumoniae and a single K. oxytoca, isolated from blood cultures in Hungary. Whole-genome sequencing and molecular typing including multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) were performed in selected strains. Gene expression of plasmid-mediated quinolone resistance determinants (PMQR) was investigated by quantitative-PCR. MLST revealed that three K. pneumoniae strains belonged to ST11 and one to ST307 whereas K. oxytoca belonged to ST52. The isolates harbored different β-lactamase genes, however, all K. pneumoniae uniformly carried blaCTX-M-15. The K. pneumoniae isolates exhibited resistance to fluoroquinolones and carried various PMQR genes namely, two ST11 strains harbored qnrB4, the ST307 strain harbored qnrB1 and all K. pneumoniae harbored oqxAB efflux pump. Levofloxacin and moxifloxacin MIC values of K. pneumoniae ST11 and ST307 clones correlated with qnr and oqxAB expression levels. The qnrA1 carrying K. oxytoca ST52 exhibited reduced susceptibility to fluoroquinolones. The maintained expression of qnr genes in parallel with chromosomal mutations indicate an additional protective role of Qnr proteins that can support dissemination of high-risk clones. During development of high-level fluoroquinolone resistance, high-risk clones retain fitness thus, enabling them for dissemination in hospital environment. Based on our knowledge this is the first report of ST307 clone in Hungary, that is emerging as a potential high-risk clone worldwide. High-level fluoroquinolone resistance in parallel with upregulated PMQR gene expression are linked to high-risk K. pneumoniae clones.
Highlights
International high-risk clones of Klebsiella pneumoniae are among the most common Gram- negative pathogens
Four K. pneumoniae and a single K. oxytoca were investigated by multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE)
International high-risk K. pneumoniae subunit A of Kpn115 (ST11) clone has been frequently detected worldwide as a successful pathogen being associated with important virulence (Damjanova et al, 2008; Andrade et al, 2014), and resistance determinants including VIM, NDM and KPC-production (Yan et al, 2002; Kristóf et al, 2010; Qi et al, 2011; Yu et al, 2016; Campana et al, 2017)
Summary
International high-risk clones of Klebsiella pneumoniae are among the most common Gram- negative pathogens. Multi-drug resistant (MDR) K. pneumoniae emerged and dramatically increased prevalence of nosocomial infections while K. oxytoca has been isolated in hospital infections with less frequency (Podschun and Ullmann, 1998; Kang et al, 2006; Zhou et al, 2016). Multi-drug resistant K. pneumoniae acquires various resistance mechanisms that confer antibiotic resistance to commonly used antibiotics. High-risk K. pneumoniae clones have acquired these antibiotic resistance determinants, that enabled them to increase their pathogenicity and survival skills. These clones have tenacity and flexibility to accumulate resistance determinants and they have contributed to disseminate global multi-drug resistance (Woodford et al, 2011). Increased diversity of plasmid-encoded antimicrobial resistance genes facilitates spread of these clones, causing significant therapeutic difficulties
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