Phenotypic and molecular analysis of staphylococcus aureus for carriage and transmission in a student population in a Malaysian public university

Staphylococcus aureus is a human commensal bacteria that colonize the skin and mucosal surfaces of healthy individuals. This opportunistic pathogen is the most common nosocomial pathogen responsible for life-threatening diseases in humans worldwide. The anterior nares are the most frequent colonization site for S. aureus and nasal carriage is a major risk factor for infections and a source of transmission of this pathogen. The incidence of S. aureus and MRSA are growing at an alarming rate not only in the healthcare settings but also in the community. In this regards, this study aims to assess the S. aureus carrier rate and persistence, risk factors for nasal carriage, antimicrobial resistance and epidemiological molecular characteristics among the university student population. A set of self-administered questionnaires on socio-demographics, hygienic practices, medical and medication history together with a consent form were distributed prior to nasal swab collection. The collection was done twice in a one month interval during October and November 2013 from 192 and 180 health sciences students, respectively, at the Faculty of Medicine and Health Sciences, Universiti Putra Malaysia. Identification of bacteria isolated was done based on basic phenotypic methods. All S. aureus isolates were subjected to antibiotic susceptibility test (AST) by Kirby-Bauer disc diffusion method against eight antibiotics and screened for MRSA by PCR detecting the mecA gene. All mecA positive isolates were subjected to staphylococcal cassette chromosome (SCC) mec typing, multilocus sequence typing (MLST) and eBURST analysis. All isolates were further characterized by spa typing, screening of PVL genes and enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR). In this study, the colonization rates of S. aureus was 31.3% (60/192) and 33.3% (60/180) of the student population during the first and second sampling respectively. Thirty-nine (65%) students were detected for S. aureus at both isolation events and referred as persistent carriers. There is no significant correlation between the carriage and the tested risk factors except for the habit of touching the nose and chronic illnesses (P