Molecular surveillance of methicillin-susceptible Staphylococcus aureus (MSSA) isolated over a one-year period from a Malaysian Teaching Hospital.

Introduction We report the results of a molecular surveillance study carried out on methicillinsusceptible Staphylococcus aureus (MSSA) isolated in a one-year duration from Hospital Canselor Tuanku Muhriz (HCTM), a tertiary hospital located in Kuala Lumpur, Malaysia. Methods The first strain isolated from each MSSA infection in HCTM during the year 2009 was included into the study. Antimicrobial susceptibility testing and agr group typing were carried out for all strains; virulence gene (cna, seh, TSST-1 and PVL) typing results of the strains were obtained from a previous study. Pulsed-field gel electrophoresis (PFGE) was done on selected strains from the orthopedic ward. Relationship(s) between different typing methods used in the study was investigated, where a p value of <0.05 indicated significant association between typing methods. Results A total of 880 MSSA strains were included into the study. The strains were generally susceptible to most antibiotics, with most of them carrying cna and agr -I (51.6%, n=454; 39.8%, n=350, respectively). A total of 17 PFGE pulsotypes were identified using an 80% similarity cut-off value, where the main pulsotype (pulsotype E) consisted of 24 isolates (23.5%). agr -III strains were found to be usually positive for both cna and seh (p<0.05). In addition, some PFGE pulsotypes were also characteristic of certain virulence genes or agr groups. Conclusions We did not identify a dominant MSSA clone circulating in HCTM in 2009. Nevertheless, results from this molecular surveillance will provide good baseline data for the hospital's second S. aureus surveillance planned for the year 2020. [ABSTRACT FROM AUTHOR]