RESUMO
OBJECTIVE: Neonates represent a high risk population for infections by coagulase-negative staphylococci (CNS). To have a better understanding of these process our purpose was to compare the expected result of the bacterium-host interaction given by the neonates' risks factors and the micro-organisms' virulence factors with the condition of infecting or colonising strain that emerge from the diagnosis on the basis of the clinical symptoms. METHODS: We studied 24 neonates who were submitted to an epidemiological control establishing as risk factors: catheters, vesicle sounds, previous surgery and immunodepressed conditions. In the CNS recovered from clinical samples we determined the following virulence factors: synergistic hemolysis, slime production, adherence to Teflon catheters and hydrophobicity. RESULTS: We found correlation between the clinical diagnosis and the expected result of the bacterium-host interaction in 21 patients (87.5%). Among them, in 8 patients infection didn't occurred in spite of having the micro-organisms 3 from 4 virulence factors since the patients didn't have risk factors. CONCLUSIONS: A microbiological study based entirely on identification and treatment can alter the biological context. It is necessary to understand the bacterium-host interaction for an appropriate comprehension of the bacterial diseases.
Assuntos
Infecções Estafilocócicas/microbiologia , Staphylococcus/patogenicidade , Aderência Bacteriana , Coagulase , Interações Hospedeiro-Parasita , Humanos , Recém-Nascido , Fatores de Risco , Staphylococcus/enzimologia , VirulênciaRESUMO
Epidemiological studies of Streptococcus agalactiae strains have been limited by the lack of sensitive and discriminatory methods for comparing clinical isolates. Serotyping, albeit a widely used methodology, has been shown to possess low capability to distinguish between epidemiologically related and unrelated isolates. We have employed here a random amplification of polymorphic DNA (RAPD) assay, using degenerate oligonucleotides as primers, to characterize S. agalactiae isolates from related or unrelated clinical samples. Epidemiologically-related isolates (mother-infant pairs) showed identical profiles by this methodology. On the contrary, 12 epidemiologically-unrelated isolates (classified into 5 different serotypes) resulted in 11 distinct RAPD patterns. This suggests that the proposed modified RAPD assay provides a highly discriminatory tool for the analysis of genomic diversity among isolates from pathogenic organisms.
Assuntos
Técnica de Amplificação ao Acaso de DNA Polimórfico , Streptococcus agalactiae/isolamento & purificação , Primers do DNA , Feminino , Genoma Bacteriano , Humanos , Recém-Nascido , Reação em Cadeia da Polimerase , Gravidez , Sorotipagem , Streptococcus agalactiae/classificação , Streptococcus agalactiae/genéticaRESUMO
Epidemiological studies of Streptococcus agalactiae strains have been limited by the lack of sensitive and discriminatory methods for comparing clinical isolates. Serotyping, albeit a widely used methodology, has been shown to possess low capability to distinguish between epidemiologically related and unrelated isolates. We have employed here a random amplification of polymorphic DNA (RAPD) assay, using degenerate oligonucleotides as primers, to characterize S. agalactiae isolates from related or unrelated clinical samples. Epidemiologically-related isolates (mother-infant pairs) showed identical profiles by this methodology. On the contrary, 12 epidemiologically-unrelated isolates (classified into 5 different serotypes) resulted in 11 distinct RAPD patterns. This suggests that the proposed modified RAPD assay provides a highly discriminatory tool for the analysis of genomic diversity among isolates from pathogenic organisms.