Abstract
Objective: To review the expression of virulence factors of Staphylococcus aureus, enabling the organism to adapt, colonize, and evade immune defences to survive in the host and cause diseases.
Methodology: Using the terms Staphylococcus aureus, virulence factors, NETs, biofilm, MRSA, SCV, superantigens, TSST, phagocytosis, a thorough search was conducted across PubMed and Google Scholar. There was no set time limit for this search; however, the articles published during the last 20 years were given preference.
Results: S. aureus is a skin commensal, colonizing the moist areas of the skin, and 20% of any given population has nasal colonization, which precedes infection. Phenotypic adaptations are observed in colonization and chronic infections, like cystic fibrosis. Stepwise changes occur in the genetic loci, resulting in different stages of colonization and infection; the earliest one to occur is in the agr locus. Colonization is mainly determined by environmental factors. Genetic makeup has generally played an important role. Elimination of nasal carriage can be a major factor in preventing S. aureus infections. The organism displays a great ability to evade the immune system by neutralizing neutrophilic killing, forming biofilms, and forming small colony variants (SCV).
Conclusion: S. aureus remains a persistent skin commensal and a very successful pathogen. The complex and poorly understood interaction between its virulence mechanisms, their regulatory system, and host factors poses a formidable challenge to the medical profession. Greater understanding of the selective production of the virulence factors and their regulation depending on the environmental challenges is required to reduce the disease burden posed by this organism.

Key words: Staphylococcus aureus, biofilm, MRSA, nasal carriage, SCV, superantigens, TSST, virulence factors.