Antifungal susceptibilities, biofilms, phospholipase and proteinase activities in the Candida rugosa complex and Candida pararugosa isolated from tertiary teaching hospitals.

PURPOSE

Non-albicansCandida species have emerged as fungal pathogens that cause invasive infections, with many of these species displaying resistance to commonly used antifungal agents. This study was confined to studying the characteristics of clinical isolates of the C. rugosa complex and C. pararugosa species.

METHODOLOGY

Seven isolates of the C. rugosa complex and one isolate of C. pararugosa were obtained from two tertiary referral hospitals in Malaysia. Their antifungal susceptibilities, biofilm, proteinase, phospholipase, esterase and haemolysin activities were characterized. Biofilms were quantified using crystal violet (CV) and tetrazolium (XTT) reduction assays at 1.5, 6, 18, 24, 48 and 72 h.Results/Key findings. The E-test antifungal tests showed that both species have elevated MICs compared to C. albicans and C. tropicalis. The highest biomass was observed in one of the C. rugosa isolates (0.237), followed by C. pararugosa (0.206) at 18 h of incubation. However, the highest bioactivity was observed in the C. rugosa ATCC 10571 strain at 24 h (0.075), followed by C. pararugosa at 48 h (0.048) and the same C. rugosa strain at 24 h (0.046), with P<0.05. All isolates exhibited high proteinase activity (+++) whereas six isolates showed very strong esterase activity (++++). All the isolates were alpha haemolytic producers. None of the isolates exhibited phospholipase activity.

CONCLUSION

Elevated MICs were shown for the C. rugosa complex and C. pararugosa for commonly used antifungal drugs. Further studies to identify virulence genes involved in the pathogenesis and genes that confer reduced drug susceptibility in these species are proposed.