The Firmicutes bacteria participate extensively in virulence and pathological processes. Enterococcus faecalis is a commensal microorganism; however, it is also a pathogenic bacterium mainly associated with nosocomial infections in immunocompromised patients. Iron-sulfur [Fe-S] clusters are inorganic prosthetic groups involved in diverse biological processes, whose in vivo formation requires several specific protein machineries. Escherichia coli is one of the most frequently studied microorganisms regarding [Fe-S] cluster biogenesis and encodes the iron-sulfur cluster and sulfur assimilation systems. In Firmicutes species, a unique operon composed of the sufCDSUB genes is responsible for [Fe-S] cluster biogenesis. The aim of this study was to investigate the potential of the E. faecalis sufCDSUB system in the [Fe-S] cluster assembly using oxidative stress and iron depletion as adverse growth conditions. Quantitative real-time polymerase chain reaction demonstrated, for the first time, that Gram-positive bacteria possess an OxyR component responsive to oxidative stress conditions, as fully described for E. coli models. Likewise, strong expression of the sufCDSUB genes was observed in low concentrations of hydrogen peroxide, indicating that the lowest concentration of oxygen free radicals inside cells, known to be highly damaging to [Fe-S] clusters, is sufficient to trigger the transcriptional machinery for prompt replacement of [Fe-S] clusters.

INTRODUÇÃO: Listeria monocytogenes é um microrganismo que se encontra disseminado na natureza, sendo responsável por causar listeriose, uma doença infecciosa causada pelo consumo de alimentos contaminados. MÉTODOS: A análise molecular de 19 linhagens de Listeria monocytogenes, sorovares 1/2a, 1/2b, 4b, 4c, isoladas de produtos lácteos do Rio Grande do Sul, Brasil. As técnicas moleculares aplicadas foram: Amplificação Randômica do DNA Polimórfico e Análise por Enzimas de Restrição. Além da análise molecular foi realizado o perfil de resistência antimicrobiana. RESULTADOS: As linhagens estudadas mostraram baixo grau de diversidade, em relação ao perfil de resistência antimicrobiana desses microrganismos das amostras analisadas todas foram susceptíveis aos antimicrobianos testados. CONCLUSÕES: As técnicas moleculares estudadas apresentaram um bom poder de discriminação para as linhagens estudadas. Além disso, todas as amostras analisadas foram susceptíveis aos antimicrobianos analisados.

INTRODUCTION: Listeria monocytogenes is a ubiquitous microorganism in nature and is responsible for listeriosis, an infectious disease caused by consumption of contaminated food. METHODS: Molecular characterization was performed on 19 strains of Listeria monocytogenes (serovars 1/2a, 1/2b, 4b and 4c), isolated from dairy products in Rio Grande do Sul, Brazil. The molecular techniques applied were random amplification of polymorphic DNA and restriction enzyme analysis. In addition to the molecular analysis, the antimicrobial resistance profile was determined. RESULTS: The strains studied showed a low degree of diversity. In relation to the antimicrobial resistance profile of those microorganisms from the samples analyzed, all of them were susceptible to the antimicrobials tested. CONCLUSIONS: The molecular techniques that were used presented good discriminatory power for the strains studied. Furthermore, all of the samples that were analyzed were susceptible to the antimicrobials tested.

Cinqüenta e seis cepas de Enterococcus spp. foram isoladas de alimentos no Sul do Brasil, confirmados por PCR e classificadas como Enterococcus faecalis (27), Enterococcus faecium (23) e Enterococcus spp. (6). Testes de susceptibilidade aos antimicrobianos demonstraram fenótipos de resistência a uma gama de antibióticos administrados em humanos, como gentamicina, estreptomicina, ampicilina e vancomicina.

Fifty-six Enterococcus spp. strains were isolated from foods in Southern Brazil, confirmed by PCR and classified as Enterococcus faecalis (27), Enterococcus faecium (23) and Enterococcus spp(6). Antimicrobial susceptibility tests showed resistance phenotypes to a range of antibiotics widely administrated in humans such as gentamycin, streptomycin, ampicillin and vancomycin.