RESUMO
The presence and characterisation of plasmid-mediated fosfomycin resistance determinants were investigated among 45 clinical vancomycin-resistant enterococci (VRE) isolated in Zhejiang Province, China. In total, 19 VRE were resistant to fosfomycin, of which 18 isolates had conjugative fosfomycin resistance and were positive for fosB. No reported fos genes were detected in the remaining isolate. Among the 18 fosB-carrying isolates, the fosB gene was always flanked by tnpA, suggesting the same novel fosB transposon. In 10 of the 18 fosB-carrying isolates, the fosB and tnpA genes were found reversely inserted in the vanA transposon Tn1546. In the remaining eight isolates the fosB and vanA genes were located on different plasmids. These findings indicate that acquisition of the conjugative plasmid harbouring the novel fosB transposon (ISL3-like transposon) and the Tn1546-like transposon (containing vanA and fosB) may explain, at least in part, the recent increase in fosfomycin-resistant Enterococcus faecium in China.
Assuntos
Enterococcus/genética , Fosfomicina/farmacologia , Plasmídeos/genética , Proteínas Proto-Oncogênicas c-fos/genética , Resistência a Vancomicina/genética , Antibacterianos/farmacologia , Proteínas de Bactérias/genética , Carbono-Oxigênio Ligases/genética , Conjugação Genética , Elementos de DNA Transponíveis , Farmacorresistência Bacteriana/genética , Enterococcus/efeitos dos fármacos , Enterococcus/isolamento & purificação , Infecções por Bactérias Gram-Positivas/tratamento farmacológico , Humanos , Testes de Sensibilidade Microbiana , Tipagem de Sequências Multilocus , Plasmídeos/efeitos dos fármacos , Transposases/genética , Vancomicina/farmacologiaRESUMO
This study reports an infectious case involving an (NDM-1)-producing Citrobacter freundii and further explored the potential threat of the bla(NDM-1) gene by analysing the characteristics of the (NDM-1)-encoding plasmid sequence. A bla(NDM-1)-positive C. freundii with high resistance to carbapenems was separated from a clinical patient suffering from a urinary tract infection. S1 nuclease-based plasmid analysis followed by Southern blot hybridization, a conjugation experiment and electrotransformation confirmed that the bla(NDM-1) gene was located on a plasmid. High-throughput sequencing of the bla(NDM-1)-positive plasmid (pCFNDM-CN) showed that it was a 54 kb IncX-type plasmid and contained a backbone region and a variable region with two ß-lactamase genes (bla(NDM-1) and bla(SHV-12)). The NDM-1 composite transposon in the variable region was surrounded by IS26 and IS5-truncated ISAba125, and shared a high sequence similarity to the bla(NDM-1) surrounding structure in Acinetobacter spp. Our research suggested that the NDM-1 composite transposon might play an essential role in mobilization of the bla(NDM-1) gene from Acinetobacter spp. to Enterobacteriaceae.
Assuntos
Citrobacter freundii/genética , Plasmídeos/genética , beta-Lactamases/genética , Acinetobacter/genética , Antibacterianos/farmacologia , Sequência de Bases , Citrobacter freundii/enzimologia , Citrobacter freundii/isolamento & purificação , Conjugação Genética , Elementos de DNA Transponíveis , Infecções por Enterobacteriaceae/diagnóstico , Transferência Genética Horizontal , Genes Bacterianos , Variação Genética , Humanos , Masculino , Pessoa de Meia-Idade , Plasmídeos/metabolismo , Infecções Urinárias/microbiologia , beta-Lactamases/metabolismoRESUMO
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. CONCLUSION: 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.
Assuntos
Acinetobacter baumannii/efeitos dos fármacos , Acinetobacter baumannii/enzimologia , Proteínas de Bactérias/genética , Metiltransferases/genética , beta-Lactamases/genética , Acinetobacter baumannii/genética , Farmacorresistência Bacteriana , Eletroforese em Gel de Campo Pulsado , Humanos , Imipenem/farmacologia , Testes de Sensibilidade MicrobianaRESUMO
A carbapenem-resistant isolate of Klebsiella pneumoniae producing class A carbapenemase KPC-2 was identified in Zhejiang, China. The KPC-2 gene was located on an approximately 60-kb plasmid in a genetic environment partially different from that of blaKPC-2 in the isolates from the United States and Colombia.