Surface Carrier Testing of Hospital Antiseptics Against Candida parapsilosis from Healthcare Workers' Hands.

Candida parapsilosis is a major cause of healthcare-associated infections due to its persistence on abiotic surfaces and efficient transmission via healthcare workers' hands. This study evaluated the antifungal efficacy and safety of clinically relevant antiseptics against 60 C. parapsilosis clinical isolates using a surface carrier test designed to simulate contamination and disinfection events on hospital surfaces. Antifungal activity was assessed by logarithmic reduction (log10) assays on surface carriers and by minimum inhibitory concentration (MIC) testing. Potential synergistic interactions between antiseptics and selected phytochemicals were investigated using checkerboard assays, and toxicity was evaluated in vivo using Caenorhabditis elegans. Surface carrier assays showed that 70% ethanol and 0.5% alcoholic chlorhexidine (CHG) achieved the highest fungicidal activity, with reductions of up to 5 log10 after 1 min exposure at 25 °C. Polyhexamethylene guanidine hydrochloride (PHMGH) displayed consistently low MIC values (0.4-0.9 ppm) and intermediate surface activity. CHG combined with eugenol or menthol produced strong synergistic interactions, reducing CHG MICs from up to 6250 ppm to as low as 20 ppm (>300-fold). Toxicity assays revealed a narrow safety margin for CHG, whereas PHMGH showed a more gradual concentration-dependent toxicity profile. These findings highlight clinically relevant differences in antiseptic performance and identify combination strategies that may reduce CHG exposure while maintaining antifungal efficacy.