The Staphylococcus aureus bacteria is widely prevalent in the environment, and can cause skin infections such as abscesses in susceptible individuals. It is spread by direct contact with infected patients or with the approximately 25 percent of the general population who are asymptomatic carriers, according to "Current Medical Diagnosis & Treatment." Methicillin-resistant strains of Staph aureus, or MRSA, typically result in more aggressive infections and require specialized treatment. Different antibiotics are used depending on whether the infection is uncomplicated, complicated, nonresistant or resistant.
Uncomplicated Nonresistant
An uncomplicated Staph aureus infection involves a small, localized area of inflammation without extensive skin involvement or spread to other organs. "Fitzpatrick's Dermatology in General Medicine" states that this will typically be in the form of folliculitis, or inflammation of the follicles; impetigo, or a contagious skin infection; or a small abscess. If the bacteria is not believed to be MRSA--because of low local prevalence or negative cultures--oral antibiotics such as the penicillin derivative dicloxacillin or the first-generation cephalosporin cephalexin may be sufficient.
Complicated Nonresistant
A complicated Staph aureus infection involves deep tissues, blood or large areas of skin. Oral antibiotics may not be sufficiently strong to contain this amount of spread, in which case parenteral therapy is indicated. Parenteral therapy is any medication which does not rely on the gastrointestinal tract for absorption. Typically, these are intravenous or intramuscular injections. These may include the penicillins nafcillin or oxacillin, or the first-generation cephalosporin cefazolin.
Uncomplicated MRSA
If it is assumed or determined that the infection involves a methicillin-resistant strain of Staph aureus, more aggressive treatments will be indicated. The bacteria must be tested in a lab to determine which antibiotics will be most effective. For uncomplicated infections, the drugs of choice, according to "Current Medical Diagnosis & Treatment," will typically be oral medications such as clindamycin, the tetracycline derivatives doxycycline or minocycline, or trimethoprim-sulfamethoxazole.
Complicated MRSA
A complicated MRSA infection can be a serious concern. As of 2010, the first-line treatment is IV administration of vancomycin, a powerful but potentially dangerous drug. However, according to the November 2007 issue of "The American Journal of Surgery," the minimum inhibitory concentration of vancomycin for the treatment of Staph skin infections has been increasing in recent years. This means that it takes higher dosages of the drug to successfully treat the infections. Therefore, MRSA is becoming resistant to vancomycin as well. Alternatives are expensive, and include linezolid and daptomycin.
References
- "Current Medical Diagnosis & Treatment 2010, Forty-Ninth Edition"; Stephen J. McPhee, Maxine A. Papadakis (eds.); 2010
- "Fitzpatrick's Dermatology in General Medicine"; Klaus Wolff, et al.; 2008
- "The American Journal of Surgery"; Increasing incidence of methicillin-resistant Staphylococcus aureus skin and soft-tissue infections: reconsideration of empiric antimicrobial therapy; Samir S. Awad M.D., et al.; May 25, 2007
