Staphylococcus aureus causes a wide variety of infections. Its growing resistance to antibiotics has raised concerns about more serious outcomes. Methicillin-resistant Staphylococcus aureus, known as MRSA, has become the most common strain in some areas. Emily A. Morrell, BA, of Harvard Medical School and Daniel M. Balkin, BA, of Yale University School of Medicine provided a review.
Staphylococcus was the bacteria in the Petri dish contaminated by mold that led Alexander Fleming to the discovery of penicillin in 1928. Penicillin was commercialized in the 1940s, and the bacteria developed resistance shortly afterward.
In 1959, the British company Beecham introduced methicillin, which is a derivative of penicillin with bulky chemical units that protect the molecule from attack by bacterial enzymes. Some strains of Staphylococcus aureus developed resistance to methicillin within a few years, but MRSA remained rare until recently.
In 1974, only 2 percent of Staphylococcus aureus (staph) infections in hospital intensive care units were methicillin resistant. By 2004, the number was 64 percent.
Antibiotics used to treat MRSA include clindamycin, tetracyclines, trimethoprim-sulfamethoxazole, linezolid, vancomycin, daptomycin, and teicoplanin. “Currently, little clinical evidence exists regarding the efficacy of alternative agents,” Morell and Balkin reported.
Staphylococcus aureus strains are found as harmless commensal bacteria in 30 percent of the human population. Some strains colonize the skin, and can produce infection if the skin barrier is disrupted through abrasion, burns, or other skin injury. Infection is more likely when the immune system is compromised.
Morrell And Balkin listed steroid use, genetic diseases, and HIV as examples of immunosuppressive conditions. Skin infections are the most common type of staph infections. If the bacteria penetrates deeper into the body, it can produce limb-threatening or life-threatening infections including sepsis, septic arthritis, osteomyelitis, and endocarditis.