Staphylococci, also known as staph, are widespread in nature, their normal habitats being the human skin and mucous membranes. Staphylococcus aureus is the most common type of staph that can cause both superficial and deep pus-forming infections. Neonates, nursing mothers, patients with influenza, chronic lung disorders and those receiving steroids or immunosuppressants are predisposed to staphylococcal infections. Antibiotics are the mainstay of therapy and the type and dosage depend on the infection site, patient condition and the resistance patterns of the strains involved.
Penicillin
The first penicillin antibiotic was isolated in 1929 and since then, this class of antibiotics have become the preferred drugs to treat staph infections. They can be taken orally, intramuscularly, or intravenously depending on the condition of the patient.
According to the Merck Manuals Online Medical Library, most of the community-acquired staphylococcal strains today produce an enzyme called beta-lactamase that can inhibit the action of penicillins. Thus, these strains are resistant to traditional penicillins such as penicillin G and ampicillin. Penicillinase-resistant penicillins like methicillin, oxacillin and cloxacillin can be used to treat such staph infections.
The National Nosocomial Infections Surveillance System, however, found out that about about 60 percent of hospital acquired staph strains in 2003 were resistant to methicillin. Dr. Henry F. Chambers stated in the April 2001 edition of "Emerging Infectious Diseases" that methicillin-resistance was becoming more common in community-acquired staph infections as well. Hence, the effectiveness of penicillins should be verified using antimicrobial assays before prescribing them to treat staph infections.
Another major limiting factor for the use of penicillins is the high incidence of reported allergy. The University of Texas Medical Branch reports that 5 percent of the population may be allergic to this class of antibiotics, the most common side effect being rash.
Cephalosporins
First generation cephalosporins such as cefazolin are effective against many different staph species. The fourth generation cephalosporin cefepime, also, has a broad spectrum of activity and is effective against staph infections. Most methicillin-resistant Staphylococcus aureus, or MRSA, strains, however, are resistant to cephalosporins as well.
Vancomycin
Vancomycin is very effective against staph infections. It penetrates most tissues well, including the blood-brain barrier. In an article published in the December 2005 edition of "American Family Physician," Dr. David Bamberger warns against the use of vancomycin to treat methicillin-susceptible Staphylococcus aureus infections unless the patient has penicillin allergy. Vancomycin is the drug of choice to treat severe MRSA infections, however, and is used only intravenously because it is not absorbed well when administered orally.
Trimethoprim/Sulfamethoxazole
Although vancomycin is considered superior to trimethoprim/sulfamethoxazole, or TMP/SMX, for staphylococcal infections, oral TMP/SMX can be used to treat mild staph infections in outpatient settings. In a document published on its website, however, Ohio State University researchers warn of serious side effects in orthopedic implant patients due to high dose long-term use of TMP/SMX.
References
- Merck Manuals: Staphylococcal Infections
- "Emerging Infectious Diseases"; The Changing Epidemiology of Staphylococcus aureus?; Henry F. Chambers; March-April 2001
- UTMB: Antibiotics 2005—An Update
- "American Family Physician"; Management of Staphylococcus aureus Infections; David M. Bamberger and Sarah E. Boyd; December 2005
- OHSU: Oral Trimethoprim-Sulfamethoxazole for MRSA Infections
