Comparison of chronic wound culture techniques: swab versus curetted tissue for microbial recovery

Health-care professionals are increasingly relying on wound cultures as part of their clinical assessment. Tissue viability nurses in the UK use wound swabbing as the standard specimen-taking technique, but others are used globally and there is no worldwide standard. This study compares two wound culture techniques in uninfected chronic wounds of active and former injection drug users seeking care through a civic needle exchange mobile wound clinic. For each wound, two sampling approaches were applied during the same visit: swab culture and curetted tissue culture. A total of 12 chronic wounds were assessed among 9 patients, including 19 swab cultures and 19 tissue cultures. These 38 cultures grew a total of 157 individually identified bacterial organisms, including 27 anaerobic organisms (17.2%), 63 Gram-positive species (40.1%), and 67 Gram-negative species (42.7%). The swab technique yielded a greater percentage recovery rate of anaerobic (55.6%), Gram-positive (52.4%), and all species (51.6%) compared to tissue culture (P>0.05). Recovery of common wound species, such as methicillin-sensitive Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, and Pseudomonas aeruginosa was the same using either method (50.0%). Swab and curetted tissue cultures yielded similar recovery rates for common wound bacteria. Therefore, swabs (including a vacuum transport container) may offer an advantage in the recovery of anaerobes. Based upon this analysis, the swabbased culture method for chronic wounds currently used in the UK is reasonable.