Detection of methicillin resistance and various virulence factors in staphylococcus aureus strains isolated from nasal carriers

Abstract

Background: Staphylococus aureus can be found as acommensal on skin and nasal flora or it may cause localand invasive infections. S. aureus has a large number ofvirulence factors. Aims: To investigate the methicillin resistance and frequen- cy of various virulence factors in S. aureus nasal isolates. Study Design: Descriptive study. Methods: Nasal samples collected from universitystudents were cultured in media. S. aureus was iden- tified by conventional methods and the Staphyloslidelatex test (Becton Dickinson, Sparks, USA). Antibioticsusceptibility tests were conducted, and the methicil- lin resistance was determined. The mecA, nuc, pvl andstaphylococcal toxin genes were examined by poly- merase chain reaction (PCR). Results: S. aureus was isolated in 104 of 600 (17.3%)nasal samples. In total, 101 (97.1%) S. aureus isolateswere methicillin-sensitive and the remaining 3 (2.9%) were methicillin-resistant. Furthermore, all but fiveisolates carried at least one staphylococcal enterotox-in gene, with seg being predominant. The tst and etagenes were determined in 29 (27.9%), and 3 (2.9%)isolates, respectively. None of the S. aureus isolatesharbored see, etb, and pvl genes.Conclusion: A moderate rate of S. aureus carriage and lowfrequency of MRSA were detected in healthy students. S.aureus isolates had a high prevalence of staphylococcalenterotoxin genes and the tst gene. In this study, a largenumber of virulence factors were examined in S. aureusnasal isolates, and the data obtained from this study can beused for monitoring the prevalence of virulence genes inS. aureus strains isolated from nasal carriers.