Numerous clumps of methicillin-resistant Staphylococcus aureus bacteria, commonly referred to by the acronym MRSA. Recently recognized outbreaks or clusters of MRSA in community settings have been associated with strains that have some unique microbiologic and genetic properties compared to the traditional hospital-based MRSA strains. This suggests that some biologic properties, e.g., virulence factors like toxins, may allow the community strains to spread more easily or cause more skin disease. A common strain named USA300-0114 has caused many such outbreaks in the United States. Staphylococcus aureus bacteria are found on the skin of all individuals; however, MRSA is a strain of these bacteria that has become resistant to certain antibiotics. Magnified 9560x.