Introduction. The soaring resistance of Klebsiella pneumoniae to fluoroquinolones in PR China has substantially limited the application of these antimicrobials, especially in those clinical settings that were threatened by persistent carbapenem-resistant K. pneumoniae (CRKP), necessitating strict implementation of antimicrobial stewardship and active enhanced surveil-lance of infection control. Hypothesis. There is interplay between plasmid-mediated quinolone resistance (PMQR) determinants and quinolone resistance -determining region (QRDR) mutations during the acquisition of a clinically important fluoroquinolone resistance (CI -FR) profile in multidrug-resistant K. pneumoniae (MDR- KP) isolates. Aim. To investigate the high -risk CRKP clones responsible for nosocomial spread and analyse the molecular patterns of CI -FR in MDR- KP isolates in a tertiary hospital in Shanghai, PR China. Methodology. A total of 34 isolates, including 30 CRKPs, were molecularly characterized. Investigations included antimicrobial susceptibility tests, multilocus sequence typing (MLST) and wzi genotyping, PCR sequencing and phylogenetic analysis for resistance-associated genes, and clinical information retrieval from medical records. Results. Two high -risk CRKP clones, ST11-wzi64 and ST15-wzi19/wzi24, were identified as being responsible for nosocomial outbreaks in the intensive care unit (ICU) and the neurosurgery department, potentially by the respiratory route. QRDR muta-tions of both gyrA and parC were detected in isolates of ST15 (S83F/D87A/S80I), ST11 (S83I/D87G/S80I) and ST218 (D87A/ S80I), respectively. The PMQR genes, qnrS1, aac(6 ')-Ib-cr and oqxAB, were present in 32 (94.1 %) of the isolates alone or in com-bination, co-occurring with genes (bla) encoding beta-lactamases, 16S rRNA methylases and putrescine ABC permeases. AcrR, an AcrAB transcriptional repressor, was insertion-inactivated by the IS5- like element in ST11 isolates. The encoding sequences of OmpK35 and OmpK36 genes were associated with specific STs and wzi alleles. ST11, ST15-wzi19 and ST218 isolates had frameshift disruptions in OmpK35 and specific GD insertions at position 134-135 in OmpK36. The 27 isolates with clinically important ciprofloxacin resistance (MICs >= 2 mg l-1) included 25 isolates (ST15, ST11, ST218) with multiple QRDR mutations, plus 1 with only 2 PMQR determinants (ST290-wzi21) and another with an unknown resistance mechanism (ST65-wzi72). Ciprofloxacin-susceptible isolates maintained intact ompK36 genes, including two CRKPs each with ST13-wzi74 (KPC- 2 and NDM- 1 coproducers) and ST65-wzi72, plus carbapenem-susceptible isolates (ST15-wzi24, ST65-wzi72, ST107-wzi173). Conclusions. Under selective pressures, the accumulation of mutations of three types (QRDR, acrR, ompK36) and the acquisi-tion of resistance-conferring genes have continuously contributed to CI -FR in MDR- KP isolates.

BackgroundThe soaring quinolone-resistance rate of Klebsiella pneumoniae, a common pathogen in immunocompromised individuals, has seriously undermined the wide applications of antimicrobials of this class. This study aimed to investigate the emerging key contributors to quinolone-resistance in multidrug resistant K. pneumoniae (MDR-KP) isolates from a clinical setting with continuing point-source infection outbreaks in Shanghai, China. ResultsBetween January and March 2017, a total of 34 K. pneumoniae isolates, including 30 carbapenem-resistant K. pneumoniae (CRKP), were selected and characterized from a teaching hospital participating in an ongoing Bacterial Resistance Surveillance Project in Shanghai, China. Two predominant high-risk CRKP clones, ST11-wzi64 and ST15-wzi19/wzi24, caused three point-source nosocomial outbreaks in intensive care unit and/or neurosurgery department potentially by respiratory-route, promoting the co-selection and evolution of multidrug-resistant determinants. Multiple quinolone resistance-determining region (QRDR) mutations occurred in isolates of ST15 (S83F, D87A; S80I), ST11 (S83I, D87G; S80I), and ST218 (D87A; S80I). Plasmid-mediated quinolone resistance determinants, qnrS1, aac(6’)-Ib-cr, oqxAB, were detected in 32 (94.1%) isolates alone or in combination, spreading accompanied with β-lactamases (mainly, KPC-2-type carbapenemase and CTX-M-type extended-spectrum β-lactamase), 16S rRNA methylases (ArmA and RmtB), and putrescine ABC transporter permease (PotI) variants, independently of QRDR-mutations. AcrR, AcrAB transcriptional repressor, was insertion-inactivated by IS5-transposase in isolates of ST11. Thirteen ompK36 variants associated with specific ST (n=7) and wzi-allele (n=9) clustered into 10 (sub)lineages in the phylogenetic tree possibly affecting the MDR phenotype and the infection outcome of isolates. Isolates of ST11, ST15, and ST218 had frameshift disruptions in OmpK35 coupled with specific GD-insertion at position 134-135 in OmpK36, all showing distinct microevolution clusters of ompK36 genotypes. Seven quinolone-susceptible isolates kept the porin genes integral, including two each CRKPs of ST13-wzi74 (carbapenemase KPC-2 and NDM-1-coproducers) and ST65-wzi72. ConclusionsUnder selective pressures, accumulation of mutations of three types (QRDR, AcrR, OmpK36/OmpK35) and acquisition of resistance-conferring genes has been continuously contributing to quinolone-resistance in clinical MDR-KP isolates, reinforcing the importance of ongoing epidemiologic surveillance on the evolution and transmission of these isolates. Our findings provided detailed mechanistic analyses and epidemiologic implications for further infection control and antibiotic stewardship initiatives.

BackgroundThe soaring quinolone-resistance rate of Klebsiella pneumoniae, a common pathogen in immunocompromised individuals, has seriously undermined the wide applications of antimicrobials of this class. This study aimed to investigate the emerging key contributors to quinolone-resistance in multidrug resistant K. pneumoniae (MDR-KP) isolates from a clinical setting with continuing point-source infection outbreaks in Shanghai, China. ResultsBetween January and March 2017, a total of 34 K. pneumoniae isolates, including 30 carbapenem-resistant K. pneumoniae (CRKP), were selected and characterized from a teaching hospital participating in an ongoing Bacterial Resistance Surveillance Project in Shanghai, China. Two predominant high-risk CRKP clones, ST11-wzi64 and ST15-wzi19/wzi24, caused three point-source nosocomial outbreaks in intensive care unit and/or neurosurgery department potentially by respiratory-route, promoting the co-selection and evolution of multidrug-resistant determinants. Multiple quinolone resistance-determining region (QRDR) mutations occurred in isolates of ST15 (S83F, D87A; S80I), ST11 (S83I, D87G; S80I), and ST218 (D87A; S80I). Plasmid-mediated quinolone resistance determinants, qnrS1, aac(6’)-Ib-cr, oqxAB, were detected in 32 (94.1%) isolates alone or in combination, spreading accompanied with β-lactamases (mainly, KPC-2-type carbapenemase and CTX-M-type extended-spectrum β-lactamase), 16S rRNA methylases (ArmA and RmtB), and putrescine ABC transporter permease (PotI) variants, independently of QRDR-mutations. AcrR, AcrAB transcriptional repressor, was insertion-inactivated by IS5-transposase in isolates of ST11. Thirteen ompK36 variants associated with specific ST (n=7) and wzi-allele (n=9) clustered into 10 (sub)lineages in the phylogenetic tree possibly affecting the MDR phenotype and the infection outcome of isolates. Isolates of ST11, ST15, and ST218 had frameshift disruptions in OmpK35 coupled with specific GD-insertion at position 134-135 in OmpK36, all showing distinct microevolution clusters of ompK36 genotypes. Seven quinolone-susceptible isolates kept the porin genes integral, including two each CRKPs of ST13-wzi74 (carbapenemase KPC-2 and NDM-1-coproducers) and ST65-wzi72. ConclusionsUnder selective pressures, accumulation of mutations of three types (QRDR, AcrR, OmpK36/OmpK35) and acquisition of resistance-conferring genes has been continuously contributing to quinolone-resistance in clinical MDR-KP isolates, reinforcing the importance of ongoing epidemiologic surveillance on the evolution and transmission of these isolates. Our findings provided detailed mechanistic analyses and epidemiologic implications for further infection control and antibiotic stewardship initiatives.