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

<i>Staphylococcus aureus</i> (<i>S. aureus</i>), especially methicillin-resistant <i>S. aureus</i> (MRSA), remains a major public health concern. This study reports the antimicrobial resistance profiles and molecular characteristics of 31 <i>S. aureus</i> 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 <i>mec</i> (SCC<i>mec</i>) typing, Panton-Valentine leukocidin (<i>pvl</i>) toxin, pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and staphylococcal protein A (<i>spa</i>) 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 SCC<i>mec</i> type II (51.9%) and ST764 (55.6%). Five <i>spa</i> types were identified with t045 (55.6%) as the major type. All 31 <i>S. aureus</i> isolates were grouped into seven types using PFGE with the SCC<i>mec</i>II-ST764-t045 clone being the most prevalent. Overall, our findings reveal that the <i>S. aureus</i> 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.