Genetic diversity of clinical Staphylococcus aureus isolates in a tertiary care hospital in India using random amplified polymorphic DNA analysis

Background: Staphylococcus aureus is a major human pathogen whose management is complicated by antimicrobial resistance and significant genetic diversity. Effective surveillance requires practical typing methods. This study aimed to isolate and characterize clinical S. aureus isolates from a hospital in Bangalore, India, and to employ random amplified polymorphic DNA (RAPD)-PCR to decipher their genotypic diversity and relatedness. Methods: Four S. aureus isolates were obtained from different clinical specimens (sputum, nasal swab, knee exudate, and urine) and confirmed through standard biochemical tests. Genomic DNA was extracted and subjected to RAPD-PCR using five arbitrary primers. The amplicons were electrophoresed, and banding patterns were analyzed to generate a similarity matrix and a UPGMA dendrogram. Results: Biochemical characterization confirmed all isolates as S. aureus , with metabolic variations noted. RAPD analysis of 172 amplified bands revealed a high degree of genetic polymorphism (95.9%). Cluster analysis delineated the isolates into distinct genotypic groups demonstrating an overall genetic similarity of only 47%. Notably, the knee (SA-3) and urinary tract (SA-4) isolates showed the closest genetic affinity, suggesting a potential epidemiological link, while the sputum isolate (SA-1) was the most divergent. Conclusion: This study demonstrates substantial genetic diversity among S. aureus isolates within a single healthcare setting indicating a heterogeneous local population. RAPD-PCR proved to be an effective initial tool for revealing this diversity and identifying potentially related strains. The findings underscore the need for continued molecular surveillance to track the spread of distinct clones and inform effective infection control strategies.