RESUMO
Acinetobacter baumannii strain Ab5 was isolated in the year 2007 in Chile, being one of the first multidrug-resistant (MDR) cases reported in the country. Here, we present the very first draft genome sequence of an MDR Chilean strain, which shows the presence of diverse resistance and acquired virulence genes.
RESUMO
INTRODUCTION: Acinetobacter baumannii is opportunistic in debilitated hospitalised patients. Because information from some South American countries was previously lacking, this study examined the emergence of multi-resistant A. baumannii in three hospitals in Cochabamba, Bolivia, from 2008 to 2009. METHODOLOGY: Multiplex PCR was used to identify the main resistance genes in 15 multi-resistant A. baumannii isolates. RT-PCR was used to measure gene expression. The genetic environment of these genes was also analysed by PCR amplification and sequencing. Minimum inhibitory concentrations were determined for key antibiotics and some were determined in the presence of an efflux pump inhibitor, 1-(1-napthylmethyl) piperazine. RESULTS: Fourteen strains were found to be multi-resistant. Each strain was found to have the blaOXA-58 gene with the ISAba3-like element upstream, responsible for over-expression of the latter and subsequent carbapenem resistance. Similarly, ISAba1, upstream of the blaADC gene caused over-expression of the latter and cephalosporin resistance; mutations in the gyrA(Ser83 to Leu) and parC (Ser-80 to Phe) genes were commensurate with fluoroquinolone resistance. In addition, the adeA, adeB efflux genes were over-expressed. All 15 isolates were positive for at least two aminoglycoside resistance genes. CONCLUSIONS: This is one of the first reports analyzing the multi-drug resistance profile of A. baumannii strains isolated in Bolivia and shows that the over-expression of theblaOXA-58, blaADC and efflux genes together with aminoglycoside modifying enzymes and mutations in DNA topoisomerases are responsible for the multi-resistance of the bacteria and the subsequent difficulty in treating infections caused by them.
Assuntos
Acinetobacter baumannii/genética , Acinetobacter baumannii/isolamento & purificação , Farmacorresistência Bacteriana Múltipla , Genes Bacterianos , Infecções por Acinetobacter/microbiologia , Acinetobacter baumannii/efeitos dos fármacos , Acinetobacter baumannii/enzimologia , Antibacterianos/farmacologia , Proteínas da Membrana Bacteriana Externa/genética , Proteínas de Bactérias/genética , Bolívia , DNA Girase/genética , Regulação Bacteriana da Expressão Gênica , Humanos , Proteínas de Membrana Transportadoras/genética , Testes de Sensibilidade Microbiana , Mutação , Piperazinas/farmacologia , Porinas/genética , beta-Lactamases/genéticaRESUMO
Acinetobacter baumannii is an opportunistic pathogen that is frequently involved in outbreaks of infection, occurring mostly in intensive care units. The increasing incidence of carbapenem resistance in A. baumannii worldwide is a concern since it limits drastically the range of therapeutic alternatives. The most important mechanism of carbapenem resistance is the enzymatic hydrolysis mediated by carbapenemases. In A. baumannii these enzymes are usually OXA-type carbapenemases, and belong to class D according to the classification of Ambler. The OXA-type carbapenemases are divided into five subgroups, four of which correspond to acquired carbapenemases, which accounts for the distribution of genes blaOXA in different geographic areas. In this work we review the different types of OXA-type carbapenemases present in A. baumannii, emphasizing the current situation in South America with special mention to the findings in Chile.
Assuntos
Infecções por Acinetobacter/microbiologia , Acinetobacter baumannii/enzimologia , Proteínas de Bactérias/metabolismo , beta-Lactamases/metabolismo , Acinetobacter baumannii/efeitos dos fármacos , Acinetobacter baumannii/genética , Acinetobacter baumannii/isolamento & purificação , Proteínas de Bactérias/classificação , Proteínas de Bactérias/genética , Carbapenêmicos/farmacologia , Humanos , América do Sul , Resistência beta-Lactâmica , beta-Lactamases/classificação , beta-Lactamases/genéticaRESUMO
Background: Acinetobacter baumannii is an important etiological agent causing nosocomial infections. High level of resistance for different kind of antimicrobials has been observed, including ß-lactam antibiotics. This feature, chromosomal or plasmid encoded, has been associated to integrons harbouring antibiotic resistance gene cassettes. Aims: To investigate the presence of integrons among clinical isolates resistant to third generation cephalosporins (3GC). Material and methods: One hundred A. baumannii strains isolated from several Chilean hospitals were included in this study. Minimal inhibitory concentrations (MIC) of 3GC by an agar dilution method were carried out. Integrons class 1, 2 and 3 were investigated by colony blot hybridisation and confirmed by PCR. Results: High level of resistance to all assayed 3GC was observed. On the other hand, integrón class 2 was the most prevalent (77 percent of isolates) followed by integron class 1 (52 percent). Forty six percent of isolates hybridised with probes for both of them. However, no positive hybridisation was detected for integron class 3. Conclusions: Nevertheless, most isolates harboured one or both class of integron; there was no direct relationship between the presence of these genetic structures and the resistance to this kind of ß-lactam antibiotics