RESUMO
Aeromonas species are widely distributed in aquatic environments and recent studies include the genus in the emergent pathogens group because of its frequent association with local and systemic infections in immunocompetent humans. Aiming to search for virulence genes in environmental strains of Aeromonas hydrophila and Aeromonas jandaei, we designed specific primers to detect act/hlyA/aer complex and alt genes. Primers described elsewhere were used to detect ast. Eighty-seven strains previously identified using phenotypic and genotypic tests as A. hydrophila (41) and A. jandaei (46) were analysed for the presence of the virulence genes using PCR. DNA fragments of expected size were purified and directly sequenced. Among the 41 strains of A. hydrophila 70.7% (29), 97.6% (40) and 26.8% (11) possessed act/hlyA/aer complex, ast and alt genes, respectively. Among the 46 strains of A. jandaei, 4.4% (2), 0% (0) and 32.6% (15) were positive for act/hly A/aer complex, ast and alt genes, respectively. Sequencing allowed for the confirmation of amplified products using BLAST. The present work proposes a specific and rapid diagnostic method to detect the main virulence determinants of Aeromonas, a genus potentially pathogenic to humans.
Assuntos
Aeromonas/genética , Enterotoxinas/análise , Fatores de Virulência/análise , Microbiologia da Água , Aeromonas/patogenicidade , Aeromonas hydrophila/genética , Proteínas de Bactérias/análise , Proteínas de Bactérias/genética , Sequência de Bases , Primers do DNA , DNA Bacteriano/química , Enterotoxinas/genética , Exposição Ambiental/análise , Dados de Sequência Molecular , Reação em Cadeia da Polimerase , Alinhamento de Sequência , Virulência/genética , Fatores de Virulência/genéticaRESUMO
AIMS: To determine the prevalence and expression of metallo-beta-lactamases (MBL)-encoding genes in Aeromonas species recovered from natural water reservoirs in southeastern Brazil. METHODS AND RESULTS: Eighty-seven Aeromonas isolates belonging to Aeromonas hydrophila (n = 41) and Aer. jandaei (n = 46) species were tested for MBL production by the combined disk test using imipenem and meropenem disks as substrates and EDTA or thioglycolic acid as inhibitors. The presence of MBL genes was investigated by PCR and sequencing using new consensus primer pairs designed in this study. The cphA gene was found in 97.6% and 100% of Aer. hydrophila and Aer. jandaei isolates, respectively, whereas the acquired MBL genes bla(IMP), bla(VIM) and bla(SPM-1) were not detected. On the other hand, production of MBL activity was detectable in 87.8% and 10.9% of the cphA-positive Aer. hydrophila and Aer. jandaei isolates respectively. CONCLUSIONS: Our results indicate that cphA seems to be intrinsic in the environmental isolates of Aer. hydrophila and Aer. jandaei in southeastern Brazil, although, based on the combined disk test, not all of them are apparently able to express the enzymatic activity. SIGNIFICANCE AND IMPACT OF THE STUDY: These data confirm the presence of MBL-producing Aeromonas species in natural water reservoirs. Risk of waterborne diseases owing to domestic and industrial uses of freshwater should be re-examined from the increase of bacterial resistance point of view.
Assuntos
Aeromonas/enzimologia , Proteínas de Bactérias/genética , Microbiologia da Água , beta-Lactamases/biossíntese , Aeromonas/isolamento & purificação , Aeromonas hydrophila/enzimologia , Aeromonas hydrophila/isolamento & purificação , Proteínas de Bactérias/biossíntese , Brasil , Primers do DNA/genética , DNA Bacteriano/química , DNA Bacteriano/genética , Genes Bacterianos , Testes de Sensibilidade Microbiana/métodos , Dados de Sequência Molecular , Reação em Cadeia da Polimerase/métodos , Análise de Sequência de DNA , beta-Lactamases/genéticaRESUMO
A clinical Klebsiella pneumoniae isolate carrying the extended-spectrum beta-lactamase gene variants bla(SHV-40), bla(TEM-116) and bla(GES-7) was recovered. Cefoxitin and ceftazidime activity was most affected by the presence of these genes and an additional resistance to trimethoprim-sulphamethoxazole was observed. The bla(GES-7) gene was found to be inserted into a class 1 integron. These results show the emergence of novel bla(TEM) and bla(SHV) genes in Brazil. Moreover, the presence of class 1 integrons suggests a great potential for dissemination of bla(GES) genes into diverse nosocomial pathogens. Indeed, the bla(GES-7) gene was originally discovered in Enterobacter cloacae in Greece and, to our knowledge, has not been reported elsewhere.