title: Diverse prevalence of 16S rRNA methylase genes armA and rmtB amongst clinical multidrug-resistant Escherichia coli and Klebsiella pneumoniae isolates.
abstract: In this study, 112 Escherichia coli and 55 Klebsiella pneumoniae isolates with a multidrug-resistant (MDR) phenotype were collected from 2007 to 2009. All isolates simultaneously exhibited resistance to cefotaxime (or ceftazidime), ciprofloxacin (or levofloxacin) and amikacin. Plasmid-mediated 16S rRNA methylases, including armA, rmtA, rmtB, rmtC, rmtD, rmtE and npmA, were detected by polymerase chain reaction (PCR) amplification. Common β-lactamase genes, including bla(TEM), bla(SHV), bla(CTX-M), bla(PER), bla(VEB), bla(GES) and bla(OXA), as well as plasmid-mediated bla(AmpC) and plasmid-mediated quinolone resistance (PMQR) determinants, including qnrA, qnrB, qnrS, qepA and aac(6')-Ib-cr, were also screened. The transferable capacity of resistance plasmids was established by conjugation testing. The genetic relatedness of isolates was analysed by pulsed-field gel electrophoresis (PFGE). Only armA and rmtB genes were detected in this study. Data showed that 93.8% of MDR E. coli and 94.5% of MDR K. pneumoniae carried at least one of armA or rmtB. The armA and rmtB genes were present in 11.6% and 82.1% of MDR E. coli, respectively. In parallel, 58.2% and 40.0% of MDR K. pneumoniae were armA- and rmtB-positive, respectively. Furthermore, the qepA gene was present in 66.3% of rmtB-carrying MDR E. coli, but it was rarely detected in MDR K. pneumoniae. Approximately 71.9% of armA-positive MDR K. pneumoniae simultaneously co-carried qnrB and bla(DHA). Moreover, 78.1% and 63.6%, respectively, of armA-positive and rmtB-positive MDR K. pneumoniae strains harboured qnr alleles and 53.1% and 59.1% harboured aac(6')-Ib-cr. In addition, MDR E. coli strains exhibited a low prevalence of qnr alleles and aac(6')-Ib-cr. PFGE analysis revealed divergent genetic relatedness, suggesting horizontal dissemination of armA and rmtB along with common β-lactamases and PMQR determinants amongst clinical MDR E. coli and K. pneumoniae isolates.
authors: Department of Microbiology, Chinese PLA General Hospital, Beijing, China.
authors: Jiyong
authors: J
authors: Yang
authors: Liyan
authors: L
authors: Ye
authors: Weiwei
authors: W
authors: Wang
authors: Yanping
authors: Y
authors: Luo
authors: Youjiang
authors: Y
authors: Zhang
authors: Li
authors: L
authors: Han
mesh_terms: D003227:Conjugation, Genetic / Q000502:physiology; D004269:DNA, Bacterial / Q000032:analysis; D024881:Drug Resistance, Bacterial / Q000187:drug effects / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics* / Q000302:isolation & purification; D029968:Escherichia coli Proteins / Q000235:genetics*; D006801:Humans; D007711:Klebsiella pneumoniae / Q000201:enzymology / Q000235:genetics* / Q000302:isolation & purification; D008780:Methyltransferases / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D010957:Plasmids / Q000378:metabolism; D015995:Prevalence; D012336:RNA, Ribosomal, 16S / Q000378:metabolism*; D001618:beta-Lactamases / Q000235:genetics / Q000302:isolation & purification
chemical_list: D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D012336:RNA, Ribosomal, 16S; C506767:ArmA protein, E coli; D008780:Methyltransferases; C540682:RmtB protein, E coli; D001618:beta-Lactamases