Staphylococcus aureus is caused by the bacterium Staphylococcus aureus, which is a Gram-positive, facultative anaerobic bacterium commonly found on the skin and in the nasal passages of about 30% of people as part of the normal microbiota. It becomes a cause of infection when it enters the body through breaks in the skin or mucous membranes, such as cuts, wounds, or surgical sites. The bacteria can spread through direct contact with infected wounds, skin-to-skin contact, or contact with objects contaminated by an infected person. Certain conditions that compromise the immune system or skin integrity increase the risk of infection. This bacterium causes a wide range of infections including skin infections (like boils, impetigo, cellulitis), bloodstream infections, pneumonia, surgical wound infections, toxic shock syndrome, food poisoning, and more. Its ability to cause disease is enhanced by various virulence factors like toxins, enzymes, and the formation of protective biofilms. Some strains have developed resistance to multiple antibiotics, notably MRSA (methicillin-resistant Staphylococcus aureus) strains, making infections difficult to treat. In summary, Staphylococcus aureus infections are caused by the bacterium entering the body through breaks in the skin or mucous membranes and overcoming the body's defenses, often facilitated by the bacteria's virulence factors and resistance traits.
