Methicillin-resistant Staphylococcus aureus (MRSA)

Methicillin-resistant Staphylococcus aureus (MRSA)

Dirk M. Elston

Evidence Levels:  A Double-blind study  B Clinical trial ≥ 20 subjects  C Clinical trial < 20 subjects  D Series ≥ 5 subjects  E Anecdotal case reports


Management strategy

Healthcare-type strains of methicillin-resistant Staphylococcus aureus (MRSA) are associated with sepsis and are common colonists of chronic wounds, where debridement is typically the best strategy. Community-type MRSA infections typically present as an abscess or furunculosis. The most important intervention for an abscess remains surgical drainage. Purulent material can reform rapidly, so a punch or cruciate incision is advised, as it tends to remain open longer to allow adequate drainage. A curette is used to probe the wound and ensure that all pockets of purulent material have been adequately drained. Irrigation can be helpful, but packing is discouraged as purulent material often reforms behind the packing material. Evidence suggests that antibiotics are often unnecessary if an abscess is adequately drained. There are obvious reasons to avoid antibiotics when they are not needed, including the risk of Stevens–Johnson syndrome, antibiotic associated diarrhea, and selection of resistant strains.

Patients with significant surrounding cellulitis, refractory infection or systemic manifestations may require antibiotic therapy. Most community-associated (CA)-MRSA strains are sensitive to trimethoprim–sulfamethoxazole. Most strains are also sensitive to doxycycline and minocycline, but doxycycline does not penetrate well into the nares. Clindamycin resistance is emerging in many communities. For serious infections, therapy should be guided by culture and sensitivity. Vancomycin, linezolid, dalbavancin, telavancin, and daptomycin are often effective. Rifampin improves intracellular killing of bacteria by vancomycin. Quinupristin–dalfopristin and tigecycline may also be effective, but quinupristin–dalfopristin, like daptomycin, may not penetrate reliably into pulmonary tissue and tigecycline has a significant incidence of nausea. Ceptobiprole and oritavancin appear promising.

Spread occurs through skin-to-skin contact and via fomites. Decolonization may be indicated for prevention of recurrence or prevention of serious invasive disease in close contacts. The most effective decolonization regimens address the nares, intertriginous and anogenital sites, as well as eczematous skin. In some patients, gut colonization may also be an issue.

Specific investigations

Cultures should be obtained from the contents of purulent infections and resistant infections. New molecular diagnostic tests are being developed to screen for MRSA and identify genes associated with resistance.

Clinical importance of purulence in methicillin-resistant Staphylococcus aureus skin and soft tissue infections.

Crawford SE, David MZ, Glikman D, King KJ, Boyle-Vavra S, Daum RS. J Am Board Fam Med 2009; 22: 647–54.

In a study of 262 patients with purulent skin and soft tissue infections performed at the University of Chicago Medical Center, 253 (97%) contained the staphylococcal chromosomal cassette mec (SCCmec) IV and 245 (94%) contained Panton-Valentine leukocidin (pvl) genes, both common characteristics of community-associated MRSA strains. 231 of the isolated strains (88%) were susceptible to clindamycin. In contrast, among the 87 isolates from non-purulent infections, only 44% were susceptible to clindamycin.

These data suggest that, at least in Chicago, purulent MRSA infections are more likely to be caused by clindamycin-susceptible isolates.

First-line therapy

Aug 7, 2016 | Posted by in Dermatology | Comments Off on Methicillin-resistant Staphylococcus aureus (MRSA)
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