Virulence factors in vancomycin-resistant and vancomycin - susceptible Enterococcus faecalis from Brazil / Fatores de virulência em Enterococcus faecalis resistentes e suscetível à vancomicina isolados no Brasil

Enterococci are members of commensal flora of animals and insects, but are also important opportunistic pathogens. Our objective was to observe if there was any difference of virulence in several groups of E. faecalis, mainly between vancomycin-resistant E. faecalis (VREFS) of colonization and infection. VREFS and vancomycin-sensitive E. faecalis from Brazil were screened for the presence of virulence factor genes. Phenotypic assays were used to assess in vitro expression, to understand the pathogenic potential of these isolates and to determine whether a correlation exists between virulence and antibiotic resistance. Different virulence profiles were found suggesting that the disseminating clone may have generated several variations. However, our study showed that one constellation of traits appeared most commonly: gelatinase, aggregation substance and esp (GEA). These factors are important because they have been implicated in cell aggregation and biofilm formation. Biofilm formation may promote the conjugation of plasmids harboring resistance and virulence genes, enhancing the probability of entry of new resistance genes into species. Curiously, the profile GEA was not exclusive to VREFS, it was the second most observed in VSEFS isolates from colonization and infection in hospitalized patients and also from rectal swabs of healthy volunteers. Such strains appear to represent the entry gateway to new resistance genes into E. faecalis and may contribute to the spreading of E. faecalis mainly in hospitals.

Enterococci são membros da microbiota comensal de animais e insetos, mas também são importantes patógenos oportunistas. Nosso objetivo foi observar se há qualquer diferença na virulência nos diversos grupos de Enterococcus faecalis, principalmente nos E. faecalis resistente à vancomicina (VREFS) isolados de colonização e infecção. VREFS e E. faecalis sensíveis à vancomicina (VSEFS) do Brasil foram pesquisadas quanto a presença de fatores de virulência. Ensaios fenotípicos foram usados para obter a expressão in vivo, entender o potencial patogênico destas amostras e determinar se existe correlação entre virulência e resistência a antibióticos. Diferentes perfis de virulência foram encontrados sugerindo que o clone que está se disseminado pode ter gerado diversas variações. No entanto, nosso estudo mostrou que um conjunto de fatores parece ser mais comum entre as amostras: gelatinase, substância de agregação e esp (GEA). Estes fatores tem sido correlacionados com a agregação de células e formação de biofilmes. A formação de biofilme pode promover a conjugação de plasmídeos contendo genes de resistência entre as espécies. Curiosamente, o perfil GAE não foi exclusivo para VREFS, foi o segundo mais observado em amostras VSEFS provenientes de colonização e infecção em pacientes hospitalizados e também de swabs retais de voluntários saudáveis. Tais linhagens pacerem representar a "porta de entrada" para novos genes de resistência em E. faecalis e podem contribuir para a disseminação de E. faecalis principalmente nos hospitais.

Virulence factors in vancomycin-resistant and vancomycin- susceptible Enterococcus faecalis from Brazil.

Enterococci are members of commensal flora of animals and insects, but are also important opportunistic pathogens. Our objective was to observe if there was any difference of virulence in several groups of E. faecalis, mainly between vancomycin-resistant E. faecalis (VREFS) of colonization and infection. VREFS and vancomycin-sensitive E. faecalis from Brazil were screened for the presence of virulence factor genes. Phenotypic assays were used to assess in vitro expression, to understand the pathogenic potential of these isolates and to determine whether a correlation exists between virulence and antibiotic resistance. Different virulence profiles were found suggesting that the disseminating clone may have generated several variations. However, our study showed that one constellation of traits appeared most commonly: gelatinase, aggregation substance and esp (GEA). These factors are important because they have been implicated in cell aggregation and biofilm formation. Biofilm formation may promote the conjugation of plasmids harboring resistance and virulence genes, enhancing the probability of entry of new resistance genes into species. Curiously, the profile GEA was not exclusive to VREFS, it was the second most observed in VSEFS isolates from colonization and infection in hospitalized patients and also from rectal swabs of healthy volunteers. Such strains appear to represent the entry gateway to new resistance genes into E. faecalis and may contribute to the spreading of E. faecalis mainly in hospitals.

Multilocus sequence typing and analysis of putative virulence factors in vancomycin-resistant and vancomycin-sensitive Enterococcus faecium isolates from Brazil.

Enterococci are leading causes of hospital-acquired infections that are often difficult to treat because of high-level aminoglycoside and glycopeptide resistance. Vancomycin-resistant enterococci are a global problem, and have been isolated with increasing frequency in hospitals in Brazil. The objective of this study was to determine the genetic relatedness of vancomycin-resistant Enterococcus faecium (VREFM) and vancomycin-sensitive E. faecium (VSEFM) isolated from human infections and faecal sources in Brazil, and to compare these isolates with those from domesticated animals. Isolates (n = 56) were classified by multilocus sequence typing (MLST) and assessed for putative virulence traits. The acm gene was detected in 98% of all isolates. The 56 isolates studied comprised 26 different MLST types. VSEFM isolates from the faeces of pigs were found to be distinct from all human isolates characterised previously by MLST, and were assigned new sequence type (ST) numbers. VREFM isolates were represented by four different STs (ST-114, ST-17, ST-281, ST-50). Among the 26 STs identified in this study, eBURST detected three groups of STs with related allelic profiles, and 19 unrelated STs. Among E. faecium isolates from Brazil, the esp gene was restricted to vancomycin-resistant isolates. Furthermore, isolates classified as ST-17 by MLST, an epidemic strain type isolated internationally with the purK-1 gene, were found among VREFM isolates from Brazil that also harboured the esp and hyl genes.