An Overview of Capsule-Encoding Genes (cap5 & cap8) in Methicillin-Resistant Staphylococcus aureus Isolated from Clinical Samples

Staphylococcus aureus is a significant pathogenic bacterium responsible for many infections. In recent years, efforts to treat infections caused by these strains have led to the emergence of antibiotic resistance, particularly to methicillin and vancomycin.

This study investigated capsule-encoding genes in methicillin-resistant S. aureus (MRSA) isolates obtained from clinical samples in hospitals affiliated with Tehran University of Medical Sciences.

Seventy-three MRSA isolates were collected and subsequently confirmed phenotypically and biochemically. Polymerase chain reaction (PCR) was employed to study the presence of specific genes, including cap8, cap5, vanA, and mecA, which are associated with MRSA.

All 73 isolates were confirmed as MRSA based on biochemical tests and the presence of the mecA gene. The abundance of MRSA isolates was highest in wound samples (n = 21, 28.77%) and lowest in synovial fluid samples (n = 1, 1.36%). The prevalence of MRSA isolates was highest in the intensive care unit (ICU) department and lowest in the ear, nose, throat (ENT) department. The cap5 gene was identified in 32 isolates (43.84%), cap8 in 27 isolates (36.99%), and vanA in five isolates (6.84%). Among the VRSA isolates, two isolates (40%) simultaneously harbored both cap5 and cap8 genes.

Identification of capsular genotypes of MRSA clinical isolates provides significant evidence because the presence of S. aureus capsular polysaccharides (CP) offers several ways to counter antibiotic resistance and the severity of pathogenicity. Capsular polysaccharides are integral components of potential vaccine formulations against S. aureus. Furthermore, they may serve as promising strategies in the future to combat MRSA and drug-resistant VRSA strains.