Plasmid-mediated 16S rRNA methylases conferring high-level aminoglycoside resistance in Escherichia coli and Klebsiella pneumoniae isolates from two Taiwanese hospitals.
OBJECTIVE
This study was conducted to investigate the occurrence of 16S rRNA methylases that confer high-level aminoglycoside resistance in Klebsiella pneumoniae and Escherichia coli isolates from two Taiwanese hospitals and the characteristics of these isolates.


METHODS
A total of 1624 K. pneumoniae and 2559 E. coli isolates consecutively collected over an 18 month period from a university hospital and seven E. coli and eight K. pneumoniae isolates that were resistant to amikacin from a district hospital were analysed. Two 16S rRNA methylase genes, armA and rmtB, were detected by PCR-based assays. beta-Lactamase characteristics were determined by phenotypic and genotypic methods.


RESULTS
Overall, 28 armA-positive and seven rmtB-positive isolates were identified, and extended-spectrum beta-lactamases (ESBLs) were detected in 33 (94.3%) isolates. The prevalence rates of armA and rmtB at the university hospital were 0.9% (n=15) and 0.3% (n=5) in K. pneumoniae and 0.4% (n=10) and 0.04% (n=1) in E. coli. CTX-M-3, CTX-M-14, SHV-5-like ESBLs, and CMY-2 were detected alone or in combination in 21, 6, 11, and 2, respectively, of the 28 armA-positive isolates. CTX-M-14 was detected in six of the seven rmtB-positive isolates. Fingerprinting of conjugative plasmids revealed the dissemination of closely related plasmids containing both armA and bla(CTX-M-3). PFGE suggests that armA and rmtB spread by both horizontal transfer and clonal spread.


CONCLUSIONS
This is the first report of the emergence of 16S rRNA methylases in Enterobacteriaceae in Taiwan. The spread of the multidrug-resistant isolates producing both ESBLs and 16S rRNA methylases may become a clinical problem.
Department of Pathology, National Cheng Kung University Hospital, No. 138, Sheng-Li Rd, Tainan 70428. jingjou@mail.ncku.edu.tw
Jing-Jou
JJ
Yan
Jiunn-Jong
JJ
Wu
Wen-Chien
WC
Ko
Shu-Huei
SH
Tsai
Chin-Luan
CL
Chuang
Hsiu-Mei
HM
Wu
Ying-Jiun
YJ
Lu
Jau-Dai
JD
Li
D000583:Amikacin / Q000494:pharmacology; D000617:Aminoglycosides / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D003227:Conjugation, Genetic; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D006761:Hospitals; D006801:Humans; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D008780:Methyltransferases / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D010957:Plasmids / Q000235:genetics*; D013624:Taiwan; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism
D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D000583:Amikacin; D008780:Methyltransferases; C047346:16S rRNA (adenine(1518)-N(6)-adenine(1519)-N(6))-dimethyltransferase; D001618:beta-Lactamases