712WHY IS STAPHYLOCOCCUS AUREUS SUCH A SUCCESSFUL PATHOGENStaphylococcus aureus causes several infections in humans and animals. Under normal conditions, the bacterium exists as part of the normal flora on the human body and only causes infections when conditions become favourable. The genetic flexibility of the bacterium plays a vital role in its virulence. Virulence mechanisms include the production of adhesins and toxins, harmful to the host body and that facilitates the invasion of the host. The organism has also developed mechanism s that enable it to circumvent the innate immune system in both animal and human hosts. The mechanisms include the production of substances that bind to the antibodies produced by the host after an infection. The bacterium also shows antibiotic resist ance as it has the ability to mutate as well as acquire resistance genes from other drug resistant strains. This promotes its success in causing infections. This review identifies the various mechanisms used by the organism in the evasion of immune responses triggered in the host after infectionm.alissa@psau.edu.saReview712016Staphylococcus aureus,Virulence,Evasion of the immune system,Mutation,ResistanceMohammed Abdulaziz AlissaLecturer of Molecular Medical Microbiology, Department of Medical Laboratory Sciences, College of Applied Medical Sciences, Prince Sattam bin Abdulaziz University, Kingdom of Saudi Arabia