Candida albicans is an opportunistic human fungal pathogen which causes disease mainly in immunocompromised
patients. Activity of hydrolytic enzymes is essential for virulence of C. albicans and so is the capacity of these cells to undergo transition from yeast to mycelial form of growth. Ocimum sanctum is cultivated worldwide for its essential oil which exhibits medicinal properties. This work evaluates the anti-virulence activity of O. sanctum essential oil (OSEO) on 22 strains of C. albicans (including a standard strain ATCC 90028) isolated from both HIV positive and HIV negative patients. Candida isolates were exposed to sub-MICs of OSEO. In vitro secretion of proteinases and phospholipases was evaluated by plate assay containing BSA and egg yolk respectively. Morphological transition from yeast to filamentous
form was monitored microscopically in LSM. For genetic analysis, respective genes associated with morphological
transition (HWP1), proteinase (SAP1) and phospholipase (PLB2) were also investigated by Real
Time PCR (qRT-PCR). Results were analyzed using Student’s t-test. OSEO inhibits morphological transition
in C. albicans and had a significant inhibitory effect on extracellular secretion of proteinases and
phospholipases. Expression profile of respective selected genes associated with C. albicans virulence by
qRT-PCR showed a reduced expression of HWP1, SAP1 and PLB2 genes in cells treated with sub-inhibitory
concentrations of OSEO. This work suggests that OSEO inhibits morphological transition in C. albicans
and decreases the secretion of hydrolytic enzymes involved in the early stage of infection as well as
down regulates the associated genes. Further studies will assess the clinical application of OSEO and its
constituents in the treatment of fungal infection