Pathophysiology: Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterium responsible for several difficult-to-treat infections in humans. It is also called oxacillin-resistant Staphylococcus aureus (ORSA). MRSA is especially troublesome in hospitals, prisons, and nursing homes, where patients with open wounds, invasive devices, and weakened immune systems are at greater risk of nosocomial infection than the general public.S. aureus most commonly colonizes under the anterior nares.
Statistics: A population-based study of MRSA infections in San Francisco, CA in 2004 to 2005 demonstrated that 90% of MRSA infections had onset in the community with an incidence rate of 316 cases/100,000 population. There were many fewer hospital-onset infections, with an incidence of 31 cases/100,000 population (543). Furthermore, a U.S. Centers for Disease Control and Prevention (CDC) study estimated that in 2005 there were 31.8 culture-confirmed invasive MRSA infections in the United States per 100,000 population amounting to 94,360 cases in that year.
Both CA-MRSA and HA-MRSA are resistant to traditional anti-staphylococcal beta-lactam antibiotics, such as cephalexin. CA-MRSA has a greater spectrum of antimicrobial susceptibility, including to sulfa drugs,tetracyclines (like doxycycline and minocycline) and clindamycin but the drug of choice for treating CA-MRSA is now believed to be vancomycin.
Many antibiotics against MRSA are in phase II and phase III clinical trials. It has been reported that maggot therapy to clean out necrotic tissue of MRSA infection has been successful. Studies in diabetic patients reported significantly shorter treatment times than those achieved with standard treatments.