Comparison of non-invasive Staphylococcus aureus sampling methods on lesional skin in patients with atopic dermatitis

Abstract

There is evidence that Staphylococcus aureus colonisation is linked to severity of atopic dermatitis. As no gold standard for S. aureus sampling on atopic dermatitis skin lesions exists, this study compared three commonly used methods. In addition, effectiveness of standard skin disinfection to remove S. aureus colonisation from these inflamed skin lesions was investigated. In 30 atopic dermatitis patients, three different S. aureus sampling methods, i.e. detergent scrubbing, moist swabbing and tape stripping, were performed on naïve and disinfected skin lesions. Two different S. aureus selective media, mannitol salt agar and chromID agar, were used for bacterial growing. Quantifying the S. aureus load varied significantly between the different sampling methods on naïve skin lesions ranging from mean 51 to 1.5 × 10⁴ CFU/cm² (p < 0.001). The qualitative detection on naïve skin was highest with the two detergent-based techniques (86% each), while for tape stripping, this value was 67% (all on chromID agar). In comparison, mannitol salt agar was less sensitive (p < 0.001). The disinfection of the skin lesions led to a significant reduction of the S. aureus load (p < 0.05) but no complete eradication in the case of previously positive swab. The obtained data highlight the importance of the selected sampling method and consecutive S. aureus selection agar plates to implement further clinical studies for the effectiveness of topical anti-staphylococcal antibiotics. Other disinfection regimes should be considered in atopic dermatitis patients when complete de-colonisation of certain skin areas is required, e.g. for surgical procedures.

Keywords: Atopic dermatitis; Colonisation; Sampling methods; Selective media; Staphylococcus aureus.

Fig. 1

Quantitative detection of S. aureus by using different detection methods and selective media (mean and standard error of the mean values). a Quantitative detection of S. aureus by using selective media MSA (n = 30). b Quantitative detection of S. aureus by using selective media SAID (n = 21). Abbreviations: ****p < 0.0001; *p < 0.05; ns = p > 0.05; MSA, mannitol salt agar; CFU, colony-forming units of Staphylococcus aureus; SAID, Staphylococcus aureus chromID; DS, detergent scrubbing; MS, moist swabbing; TS, tape stripping; AD, atopic dermatitis

Fig. 2

Qualitative detection of S. aureus by using different detection methods and selective media. a Qualitative detection of S. aureus by using selective media MSA (n = 21). b Qualitative detection of S. aureus by using selective media SAID (n = 21). Abbreviations: ****p < 0.0001; ***p < 0.001; **p < 0.1; SA, S. aureus; MSA, mannitol salt agar; SAID, S. aureus chromID; DS, detergent scrubbing; MS, moist swabbing; TS, tape stripping; AD, atopic dermatitis