Methicillin Resistant Staphylococcus aureus (MRSA)

Staphylococcus aureus is an opportunistic pathogen often carried asymptomatically on the human body. Methicillin-resistant S. aureus (MRSA) includes those strains that have acquired a gene giving them resistance to methicillin and essentially all other beta-lactam antibiotics. MRSA was first reported in 1961, soon after methicillin was introduced into human medicine to treat penicillinresistant staphylococci. 1-5 This group of organisms has since emerged as a serious concern in human medicine. 1,2,4,5 MRSA was first reported as a nosocomial pathogen in human hospitals. Although these organisms cause the same types of infections as other S. aureus, hospital-associated strains have become resistant to most common antibiotics, and treatment can be challenging. 2,6-8 Since the 1990s, MRSA has also become a concern in people who have not been hospitalized or recently had invasive procedures; the strains that cause such infections are called community-acquired or community-associated MRSA. 2,5,9-11 Community-associated MRSA first appeared in high-risk populations such as intravenous drug users, people in nursing homes, and people who were chronically ill, but they are now reported even in healthy children. 3,10 Until recently, these strains were susceptible to many antibiotics other than beta-lactams; however, resistance seems to be increasing, and multiple antibiotic resistant strains have started to emerge. 6,10-12