Decreased Susceptibilities to Retapamulin, Mupirocin, and Chlorhexidine among Staphylococcus aureus Isolates Causing Skin and Soft Tissue Infections in Otherwise Healthy Children

Topical antimicrobial and antiseptic agents are commonly used in the management of minor skin and soft tissue infections (SSTIs). Resistance to mupirocin has been documented inStaphylococcus aureus isolates causing SSTIs. Data are limited, however, on the prevalence of retapamulin resistance or tolerance to antiseptics. We sought to determine the prevalence of decreased susceptibility to retapamulin and mupirocin as well as the potential for decreased chlorhexidine susceptibility ofS. aureus isolates from SSTIs in children. Two hundred isolates from patients with a single SSTI and 200 isolates from patients with ≥3 previous episodes from the years 2010 to 2012 were selected from anS. aureus surveillance study. Screening for retapamulin resistance was performed by the broth macrodilution method; mupirocin MICs were determined by Etest. PCR was performed for the presence of thesmr gene associated with elevated MICs/minimum bactericidal concentrations (MBCs) to chlorhexidine. Among the isolates screened, 38 isolates (9.5%) exhibited retapamulin resistance, of which 22 (57.9%) were methicillin-resistantS. aureus (MRSA). Two isolates (0.5%) displayed cross-resistance to retapamulin and linezolid. Thirty-nine isolates (9.8%) were found to have mupirocin resistance.smr -positiveS. aureus accounted for 14% of isolates. The proportion ofsmr -positive organisms increased during the study (P = 0.005). The prevalence ofin vitro resistance to topical antimicrobials amongS. aureus isolates causing SSTI in healthy children in our community is almost 10%. Retapamulin resistance was associated with cross-resistance to linezolid in 0.5% of isolates. In addition, there was an increase in the proportion ofsmr -positive isolates. Further research including clinical correlations with these findings is warranted.