Antifungal resistance and Ocimum gratissimum L. essential oil-clotrimazole interactions in clinical Candida isolates from Vietnam.

AIMS To describe Candida species distribution and antifungal susceptibility in a Vietnamese tertiary-hospital collection and to evaluate Ocimum gratissimum L. essential oil (OGEO) as an in-vitro adjunct to clotrimazole.

MATERIALS AND METHODS We retrospectively analysed 423 clinical Candida isolates collected in 2017-2018. Species identification used routine phenotypic methods/VITEK 2; susceptibility to fluconazole, voriconazole, and amphotericin B followed CLSI M27-A3. OGEO was chemically profiled by GC-MS. Crystal violet assays assessed OGEO inhibition of biofilm formation in 30 C. albicans isolates, and checkerboard assays evaluated OGEO-clotrimazole interactions in 20 species-resolved isolates using FICI.

RESULTS Species-level identification was available for 212 isolates; C. tropicalis (25.8% of the full cohort) slightly exceeded C. albicans (21.8%), while 49.8% were recorded as Candida spp. Overall fluconazole resistance was 13.7%, with higher resistance in C. tropicalis than C. albicans. OGEO was eugenol-rich (66.7%) and inhibited C. albicans biofilm biomass by 71.2% at 1% and 89.6% at 2% v/v. OGEO-clotrimazole interactions were FICI-defined synergistic in 65%, additive in 30%, indifferent in 5%, and never antagonistic.

CONCLUSION OGEO showed promising in-vitro anti-biofilm and clotrimazole-potentiating activity, supporting further standardized, species-matched, topical-formulation and safety studies.