The Value of Cleaning a Skin Ulcer Before Obtaining a Swab to Detect Staphylococcus aureus, MRSA and Streptococcus pyogenes

Accurate identification of pathogens in clinically infected skin ulcers is essential for targeted antimicrobial therapy. Although expert consensus recommends mechanical cleansing of the ulcer bed prior to swabbing, there is a lack of empirical evidence to support this practice. This study investigated the impact of mechanical cleansing with sterile cotton gauze pads saturated with isotonic saline or clean water on microbiological results. Triple swabs were collected from 106 patients with skin ulcers at two distinct time points: prior to cleansing (baseline) and immediately following mechanical cleansing. All specimens were analysed using both conventional culture and point-of-care nucleic acid amplification tests (NAAT) for Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), and Streptococcus pyogenes. S. aureus was the most prevalent isolate, with detection rates of 23%-24% by culture and 44%-45% by NAAT. The prevalence and specific bacterial findings remained highly consistent before and after mechanical cleansing, with high levels of concordance across both diagnostic modalities. A sensitivity analysis excluding patients with recent antibiotic use confirmed these findings. Our results demonstrate that mechanical cleansing of the ulcer does not significantly alter the microbiological yield or improve the detection of key pathogens. These findings suggest that the traditional requirement for pre-sampling cleansing may be unnecessary for routine diagnostic swabbing.