Staphylococcus epidermidis, despite regarded as a commensal, is recognized as a nosocomial pathogen usually by acting as an opportunist, especially in infections associated with implanted foreign body materials. Pre-operative antiseptic preparation is an important strategy for reducing the risk of complications such as surgical site infection (SSI). The currently most widely used antiseptic compounds are alcohols and quaternary ammonium compounds (QACs), predominantly chlorhexidine.
The aim of this study was to investigate if decreased susceptibility to chlorhexidine among S. epidermidis was present in our setting. S. epidermidis (n=143) were obtained from prosthetic joint infections (PJI) (n=61), commensals (n=24), post-operative infections after cardiothoracic surgery (n=31), and the skin of the chest after routine disinfection prior cardiothoracic surgery (n=27). Determination of MIC of chlorhexidine was performed on Müeller Hinton agar plates supplemented with serial dilutions of chlorhexidine. Five QAC resistance genes; qacA/B, smr, qacH, qacJ, and qacG, were detected using PCR.
Decreased susceptibility to chlorhexidine was found in 54% of PJI isolates, 68% of cardiothoracic isolates, 21% of commensals, and 7% of isolates obtained from the skin of cardiothoracic patients, respectively.
The qacA/B gene was present in 62/143 isolates (43%), smr in 8/143 (6%) and qacH in one isolate (0.7%). The qacA/B gene was found in 52% of PJI isolates, 61% of cardiothoracic isolates, 25% of commensals, and 19% of isolates obtained from the skin of cardiothoracic patients. In conclusion, decreased susceptibility to chlorhexidine as well as QAC resistance genes was highly prevalent among S. epidermidis causing deep SSIs.