Abstract
BackgroundEmergence of rmtB-positive Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae (KPC-KP) poses a great threat to antimicrobial treatment options.MethodsFrom January 2010 to December 2010, non-duplicate KPC-KP isolates from our hospital were screened for rmtB and multiple other resistance determinants with PCR. Subsequent studies included MIC determination, PFGE, and multilocus sequence typing. Records from patients with KPC-KP isolated were retrospectively reviewed. Comparisons of molecular and clinical characteristics between rmtB-positive and rmtB–negative isolates were systematically performed, as well as the environmental colonization study in ICU wards.ResultsA total of 84 KPC-KP strains were collected, including 48 rmtB-positive KPC-KP (RPKP) and 36 rmtB-negative KPC-KP (RNKP) isolates. All KPC-KP isolates were multidrug resistant, with colistin and tigecycline being the most active agents. Compared with RNKP, RPKP displayed a much severer resistance phenotype. Susceptibility rates for amikacin (0% for RPKP versus 88.9% for RNKP, p < 0.01), fosfomycin (8.5% for RPKP versus 88.9% for RNKP, p < 0.01), and minocycline (6.7% for RPKP versus 52.8% for RNKP, p < 0.01), were all significantly lower in RPKP strains. Isolates belonging to PFGE pulsetype A and sequence type 11 were predominant in both groups, including 39 (81.3%) RPKP and 22 (61.1%) RNKP isolates. Nevertheless, RNKP showed more complex genetic backgrounds compared with RPKP. Diverse clinical characteristics were found in both cohorts, however, no significant differences were observed between RPKP and RNKP patients.ConclusionsRPKP strains have spread widely and gradually replaced RNKP in our hospital. They seemed to show much severer resistance phenotypes compared with RNKP and had a bigger dissemination potential. Prudent use of available active agents combined with good control practices is therefore mandatory.
Highlights
Emergence of rmtB-positive Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae (KPC-KP) poses a great threat to antimicrobial treatment options
Our study focused on the comparisons of microbiological, molecular and clinical characteristics between rmtB-positive KPC-producing K. pneumoniae (KPC-KP) (RPKP) and rmtB-negative KPCKP (RNKP) isolates
A total of 84 KPC-KP isolates were identified during the study period
Summary
Emergence of rmtB-positive Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae (KPC-KP) poses a great threat to antimicrobial treatment options. During the past 10 years, Chinese clinicians have witnessed a dramatic increase in the rates of carbapenem resistance among clinical isolates of Klebsiella pneumoniae. 16S rRNA methylases (ArmA and RmtB) were reported in a few KPC-producing Enterobacteriaceae recently, conferring high level resistance to almost all clinically important aminoglycosides [7,8,9]. Since its first isolation in 2007 [10], KPC-KP has been increasingly emerging at our hospital Most of these isolates were still susceptible to one or more aminoglycoside antibiotics until 2009; high-level aminoglycoside resistance has emerged and gradually become prevalent in the last two years (data not shown). A small outbreak of KPCRmtB-producing K. pneumoniae was revealed in the neurosurgery department [7] This promoted us to perform a hospital-wide screening of rmtB gene in KPC-KP strains. Our study focused on the comparisons of microbiological, molecular and clinical characteristics between rmtB-positive KPC-KP (RPKP) and rmtB-negative KPCKP (RNKP) isolates
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