RESUMO
In order to understand the genetic background and dissemination mechanism of carbapenem resistance and fosfomycin resistance in Enterobacteriaceae isolates, we studied a clinical Escherichia coli strain HS102707 isolate and an Enterobacter aerogenes strain HS112625 isolate, both of which were resistant to carbapenem and fosfomycin and positive for the bla(KPC-2) and fosA3 genes. In addition, a clinical Klebsiella pneumoniae strain HS092839 isolate which was resistant to carbapenem was also studied. A 70-kb plasmid was successfully transferred to recipient E. coli J53 by a conjugation test. PCR and Southern blot analysis showed that bla(KPC-2) was located on this plasmid. The complete sequence of pHS102707 showed that this plasmid belongs to the P11 subfamily (IncP1) and has a replication gene, several plasmid-stable genes, an intact type IV secretion system gene cluster, and a composite transposon Tn1721-Tn3 that harbored bla(KPC-2). Interestingly, a composite IS26 transposon carrying fosA3 was inserted in the Tn1721-tnpA gene in pHS102707 and pHS112625, leading to the disruption of Tn1721-tnpA and the deletion of Tn1721-tnpR. However, only IS26 with a truncated Tn21-tnpR was inserted in pHS092839 at the same position. To our knowledge, this is the first report of fosA3 and bla(KPC-2) colocated in the same Tn1721-Tn3-like composite transposon on a novel IncP group plasmid.
Assuntos
Proteínas de Bactérias/genética , Enterobacter aerogenes/efeitos dos fármacos , Escherichia coli/efeitos dos fármacos , Fosfomicina/farmacologia , Klebsiella pneumoniae/efeitos dos fármacos , beta-Lactamases/genética , Antibacterianos/farmacologia , Sistemas de Secreção Bacterianos/genética , Técnicas de Tipagem Bacteriana , Sequência de Bases , Elementos de DNA Transponíveis/genética , DNA Bacteriano/genética , Farmacorresistência Bacteriana Múltipla/genética , Enterobacter aerogenes/genética , Enterobacter aerogenes/isolamento & purificação , Escherichia coli/genética , Escherichia coli/isolamento & purificação , Humanos , Klebsiella pneumoniae/genética , Klebsiella pneumoniae/isolamento & purificação , Testes de Sensibilidade Microbiana , Dados de Sequência Molecular , Tipagem de Sequências Multilocus , Plasmídeos/genética , Análise de Sequência de DNARESUMO
Fifty-seven carbapenem-resistant Klebsiella pneumoniae isolates belonging to ST11 (50 isolates), ST423 (5 isolates), and two other sequence types were studied. All were positive for blaKPC-2, blaTEM-1, and blaCTX-M-14. SDS-PAGE analysis of six representative isolates demonstrated varied porin expression. Nevertheless, when blaKPC-2 was deleted, carbapenem resistance was markedly reduced. Additionally, SHV-12, DHA-1, and/or VIM-1 appeared to contribute to accessory carbapenemase activity. In contrast, OmpK35 and/or OmpK36 deficiency seemed to serve only as a minor cooperative factor.