CA-MRSA

Community-acquired methicillin-resistant S. aureus (CA-MRSA) is becoming an increasingly common pathogen in cellulitis. CA-MRSA can be distinguished from health care-associated MRSA (HA-MRSA) by its genetic dissimilarity, host population, drug susceptibility patterns, and toxin production. 

CA-MRSA is susceptible to more antibiotics than HA-MRSA. Like HA-MRSA, CA-MRSA typically is sensitive to vancomycin, linezolid, daptomycin, tigecycline, and quinupristin/ dalfopristin, but it also may be sensitive to clindamycin, doxy-cycline, minocycline, and/or trimethoprim-sulfamethoxazole (TMP-SMX).14... 

Of the latter four agents, clindamycin has the most data supporting its use. However, the clinician must be aware of inducible clindamycin resistance. For CA-MRSA isolates determined to be resistant to erythromycin but sensitive to clindamycin, an additional laboratory analysis, known as the erythromycin-clindamycin D-zone test, is conducted to assess for inducible clindamycin resistance.15 Isolates for which the D-zone test indicates inducible resistance should not be treated with clindamycin. 

With regard to the clinical effectiveness of TMP-SMX and the tetracyclines, anecdotal evidence and small trials support their use in the treatment of CA-MRSA cellulitis. However, large randomized, controlled trials are needed to confirm their place in therapy.16,17... 

Finally, CA-MRSA produces the virulent Panton-Valentine leukcocidin toxin. It destroys leukocytes, causes severe tissue damage and necrosis, and has been associated with both necrotizing skin infections and pneumonia.14... 

If the MRSA rate at your hospital is 75% (mostly CA-MRSA), would you change your pharmacologic recommendation If so, how ... 

Oral, narrow-spectrum antibiotic therapy with activity against Staphylococcus aureus and streptococcal species. Include coverage for MRSA (HA- or CA-MRSA) according to patient history and resistance patterns in the area. 

Linezolid 600 mg by mouth every 12 hours Vancomycin 1 g IV every 12 hours Daptomycin 4 mg/kg IV daily CA-MRSA suspected ... 

The majority of SSTIs are caused by gram-positive organisms and, less commonly, gram-negative bacteria present on the skin surface. Staphylococcus aureus and Streptococcus pyogenes account for the majority of SSTIs. Community-associated methicillin-resistant S. aureus (CA-MRSA) has recently emerged and it is often isolated in otherwise healthy patients. 

Initial therapy with trimethoprim-sulfamethoxazole appears to be effective for CA-MRSA and should be considered in geographic areas in which CA-MRSA are commonly encountered. Alternative agents for documented infections with resistant gram-positive bacteria such as methicil-lin-resistant staphylococci and vancomycin-resistant enterococci include linezolid, quinupristin/dalfopristin, daptomycin, and tigecycline. 

For example, methiciUin-resistant Staphylococcus aureus (MRSA) is a strain of bacteria that has become resistant to methicUhn. In healthy individuals, the S. aureus, though present, does not cause active infection. But in the immune suppressed and the elderly, S. aureus infection can result in morbidity and mortality. Worse still is the fact that MRSA is spread in healthcare institutions and community centers such as hospitals, medical centers, nursing homes, childcare centers, gymnasiums, and confined living quarters. The terms HA-MRSA and CA-MRSA refer to hospital-associated and community-associated MRSA. 

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