Staphylococcal resistance revisited: community-acquired methicillin resistant Staphylococcus aureus--an emerging problem for the management of skin and soft tissue infections

Abstract

Purpose of review: In the community non-localized or deep staphylococcal skin and soft tissue infections are typically managed with beta-lactamase stable penicillins. The aims of this review are (1) to evaluate the evidence for the emergence of new strains of community-acquired methicillin resistant Staphylococcus aureus (MRSA), (2) to identify the reasons for their significant association with cutaneous infections, and (3) to consider how they arose and how big a threat they pose to the management of such infections outside hospitals.

Recent findings: MRSA are emerging as significant community pathogens, especially in previously healthy children with no recognizable risk factors, and are predominantly associated with skin and soft tissue infections (especially abscesses and cellulitis). When present, risk factors are generally similar to those for infection with methicillin susceptible S. aureus. The MRSA isolates associated with such infections may not be entirely 'new', but could represent the displacement of some hospital clones (e.g. EMRSA-15 or variants thereof) to the community as well as the de-novo generation of novel MRSA clones by multiple horizontal transmissions of the mecA gene into methicillin susceptible S. aureus with different genetic backgrounds, some of which are already circulating globally. Community-acquired MRSA from diverse locations are non multiresistant and almost always contain the novel type IV SCCmec commonly found in coagulase-negative staphylococci, but also in hospital-associated gentamicin susceptible MRSA from France, the paediatric clone and in EMRSA-15.

Summary: More local data on CA-MRSA infections are needed so that dermatologists and community physicians can assess the risk of such infections amongst their patients and avoid the inappropriate administration of beta-lactams. No simple change in prescribing practices will entirely alleviate selective pressure for the spread of community-acquired MRSA and not exacerbate resistance in pyogenic streptococci, commonly found together with S. aureus in skin and soft tissue infections. The importance of hygiene in preventing the spread of community-acquired MRSA in the community must be reemphasized.