Molecular Typing of Clinical, Colonizing and Environmental Staphylococcus aureus Isolates Using Multilocus Sequence Typing (MLST): A Global Comparative Analysis

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Abstract
Introduction: Staphylococcus aureus (S. aureus) is a facultative anaerobic bacterium that colonizes the nasal cavity, skin and other mucosal surfaces of humans. It causes a wide spectrum of infections, ranging from localized skin and soft tissue infections to severe systemic conditions such as bacteremia, endocarditis and osteomyelitis. The pathogen is a major contributor to hospital-acquired infections and the emergence of Methicillin-Resistant S. aureus (MRSA) poses significant therapeutic and epidemiological challenges. Methods: This retrospective analytical study analysed 100 archived S. aureus isolates from clinical, colonizing and environmental sources in a hospital setting. Multilocus Sequence Typing (MLST) was performed on 55 of these isolates. Fragments of seven housekeeping genes were amplified following the protocol outlined on the PUBMLST website. The resulting amplicons were sequenced and Sequence Types (STs) were assigned by comparing allele profiles with the PUBMLST database. Novel allelic combinations were designated as new STs. Results: The identified STs included ST22, ST5, ST364, ST1910, ST5939, ST5529, ST7442, ST672 and ST9162. Forty-four novel STs were submitted to the PUBMLST site and were designated new STs. Most of these isolates belonged to Clonal Complex 5 (CC5). A comparative analysis was conducted against Indian and global S. aureus isolates available in the PUBMLST database to assess phylogenetic relationships and geographic distribution. Conclusion: Understanding the molecular epidemiology and evolutionary dynamics of S. aureus through MLST provides valuable insights into strain diversity and transmission patterns. These findings underscore the importance of robust infection-control and targeted surveillance strategies to mitigate the spread of MRSA in healthcare settings.

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