[Study on carbapenemase and 16S rRNA methylase of imipenem-resistant Acinetobacter baumannii].
OBJECTIVE
To investigate the prevalence of 16S rRNA methylases gene in imipenem-resistant Acinetobacter baumannii isolates from China.


METHODS
A total of 342 imipenem-resistant A. baumannii isolates were collected between December 2004 and December 2005, from 25 hospitals of China. Agar dilution was used to determinate the minimal inhibitory concentration (MIC) of these isolates. The homology of these isolates was analyzed by pulse-field gel electrophoresis (PFGE). Several 16S rRNA methylase genes and carbapenemase genes were detected by PCR-based assays and PCR products were sequenced.


RESULTS
The rates of resistance to ampicillin-sulbactam, cefoperazone-sulbactam, tobramycin, and minocycline were 68.0%, 54.2%, 87.4%, and 75.9%, respectively. The rate of resistance to polymyxin E was 10.8%, the lowest among the tested agents. The rates of resistance to all other tested antimicrobial agents were more than 90%. The A. baumannii isolates belonged to 29 distinct clones. Among them, 6 clones were dominant, consisting of 303 isolates in total. All isolates contained the blaOXA-51-like gene (blaOXA-66) and 322 isolates contained the blaOXA-23-like gene. PCR with the ISAba1-OXA-23-like primers generated a PCR product in 314 isolates, and PCR with the ISAba1-OXA-51-like primers generated a PCR product in 13 strains. 221 armA-positive isolates were identified.


CONCLUSIONS
Most of the imipenem-resistant A. baumannii contained blaOXA-23, with ISAbal upstream of the gene. 16S rRNA methylase gene armA was widely distributed in these isolates. The results suggested that the spread of clones played an important role in the outbreak of imipenem-resistant A. baumannii in China.
Zhou
Hua
H
Department of Respiratory Medicine, First Affiliated Hospital, Zhejiang University, Hangzhou 310006, China.
Du
Xiao-Xing
XX
Yang
Qing
Q
Zhou
Jian-Ying
JY
Yu
Yun-Song
YS
Li
Lan-Juan
LJ
D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics*; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D006801:Humans; D015378:Imipenem / Q000494:pharmacology; D008780:Methyltransferases / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D001618:beta-Lactamases / Q000235:genetics*
D001426:Bacterial Proteins; D015378:Imipenem; D008780:Methyltransferases; C035181:rRNA (adenosine-O-2'-)methyltransferase; D001618:beta-Lactamases; C063912:carbapenemase