PURPOSE

To study antibiotic susceptibility and biofilm-forming potential of ocular isolates of Candida albicans along with gene expression.

METHODS

Seven clinical isolates of C. albicans (keratitis-6 and orbital cellulitis-1) were evaluated. Biofilm formation in one isolate was monitored by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Expression of 27 genes (real-time PCR) associated with biofilm formation and virulence was compared between biofilm-positive and biofilm-negative ocular C. albicans isolates. The temporal expression (4 to 72 hours) of the 27 overexpressed genes was also determined. Similar studies were also done with biofilm-positive and biofilm-negative nonocular C. albicans.

RESULTS

Four of seven ocular C. albicans isolates exhibited the potential to form biofilm, one of which was resistant to three antifungals, whereas three were susceptible to all. SEM studies indicated that biofilm increased from two to three adherent layers of cells at 24 hours to multiple layers by 72 hours. CLSM showed that biofilm thickness increased from 5.2 μm at 24 hours to 17.98 μm at 72 hours. Upregulation of 27 genes involved in virulence and biofilm formation was observed both in the ocular and nonocular C. albicans positive for biofilm formation and compared to the respective non-biofilm-forming C. albicans. The results also indicated similarity in expression of genes between biofilm-forming ocular and nonocular pathogenic C. albicans. Temporal expression of the 27 genes (involved in adhesion, initiation, maturation, and dispersal stages of biofilm) in the biofilm-positive ocular isolate indicated that expression pattern followed four different patterns.

CONCLUSIONS

This is the first study showing similarity in expression of genes in biofilm-forming ocular and nonocular isolates of C. albicans, suggesting that upregulated genes could serve as a potential target for developing therapeutic strategies.