Molecular Characterization of Clinical Isolates of Methicillin-Resistant Staphylococcus aureus from Chonburi, Thailand.

Staphylococcus aureus (S. aureus), especially methicillin-resistant S. aureus (MRSA), remains a major public health concern. This study reports the antimicrobial resistance profiles and molecular characteristics of 31 S. aureus isolated during 2017-2018 from inpatient and outpatient clinical specimens from Queen Sirikit Naval Hospital (QSH) in Chonburi province, Thailand. All isolates were tested for antimicrobial susceptibility. Staphylococcal cassette chromosome mec (SCCmec) typing, Panton-Valentine leukocidin (pvl) toxin, pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and staphylococcal protein A (spa) typing were performed. Twenty-seven isolates were confirmed to be MRSA and exhibited resistance to up to seven antibiotics classes. The main MLST type was SCCmec type II (51.9%) and ST764 (55.6%). Five spa types were identified with t045 (55.6%) as the major type. All 31 S. aureus isolates were grouped into seven types using PFGE with the SCCmecII-ST764-t045 clone being the most prevalent. Overall, our findings reveal that the S. aureus isolates in this study differ from previous reports in Thailand, indicating a potential shift in local strains, highlighting the need for ongoing molecular surveillance of multidrug resistance patterns of MRSA in Southeast Asia.