Swab culture of purulent skin infection to detect infection or colonization with antibiotic-resistant bacteria

Abstract

Prescribing systemic antibiotics without susceptibility testing has significant shortcomings, especially in long term care facilities with high rates of multidrug-resistant organisms (MDROs) including methicillin-resistant Staphylococcus aureus. Tissue biopsy or aspiration sampling of infected tissue is the "gold standard" for culture of skin and soft tissue infection and is especially important with serious infection, systemic toxicity, or failure of initial therapy. Swab cultures are probably the most commonly used method to determine the resistance pattern of skin pathogens treated in nursing home residents. However, they are controversial, especially when obtained from chronic wounds. The culture may be obtained from an uninfected wound and lead to unnecessary antibiotic therapy. If material superficial to the infected living tissue is sampled, colonizers may be isolated. This report is focused on swab culture obtained by the Levine technique, after debridement or cleaning down to viable tissue when an acute purulent skin infection has been diagnosed based on clinical criteria. Swab cultures should not be used to determine IF a wound is acutely infected; rather the role may be to identify potential pathogens when deep tissue biopsy is not elected. The swab culture may identify the pathogen or overlying MDRO colonization, a risk factor for MDRO infection. MDRO isolation should heighten the clinician's level of concern if the prescribed antibiotic did not "cover" the MDRO or potential pathogen that was isolated. Properly performed swab cultures could play a role in the identification of methicillin-resistant Staphylococcus/MDRO infections treated in nursing homes.