Molecular surveillance of methicillin-susceptible (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 methicillin-susceptible (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 (, , 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 and -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%). -III strains were found to be usually positive for both and (p<0.05). In addition, some PFGE pulsotypes were also characteristic of certain virulence genes or 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 surveillance planned for the year 2020.