Study the presence of virulence factors in commensal staphylococcus aureus isolates

Abstract

Staphylococcus aureus is both a human commensal and a frequent cause of clinically important infections. This bacterium produces a variety of extracellular toxins and virulence factors including Toxic Shock Syndrome Toxin-1 (TSST-1) and enterotoxins A (SEA) which is the major cause of Toxic Shock Syndrome (TSS) and food poisoning. In this study, 15 S. aureus isolates (10 from normal healthy Vietnamese people and 5 from patients of Bach Mai Hospital (Ha Noi,VietNam)) were examined for five extracellular toxins including Lipase, Protease, Lecithinase, Hemolysin and Elastase. At the same time, the presence of Staphylococcal enterotoxin A (sea) and Toxic Shock Syndrome Toxin-1 (tst) genes was also checked by using PCR method. The result showed that most of 15 S. aureus isolates (isolates from healthy human and from patients) had ability to produce all five toxins. There were 6 out of 10 commensal isolates (60%) and 4 out of 5 clinical isolates (80%) were positive for the SEA gene (sea) and none of them were positive for TSST-1 gene (tst). These results partially suggested that commensal S. aureus isolates also have high risk of infection comparable to the clinical isolates. In conclusion, our research provides further understanding on the virulence of commensal S. aureus which might be helpful in understanding the pathogenesis of community- acquired staphylococcal infection in Vietnam. Keyword: Staphylococcus aureus, virulence factors, commensal, SEA, TSST-1.