DST659 genotype of Candida albicans showing positive association between biofilm formation and dominance in Taiwan.

Based on multiple locus sequence typing, we previously found that DST659 and DST693 were dominant genotypes of Candida albicans among the bloodstream isolates at Chang-Gung Memorial Hospital at Linkou. Biofilm-forming activity, which is critical for C. albicans virulence, probably contributed to the dominance of antifungal sensitive isolates in hospital. Both in vitro membrane weighting and in vivo zebrafish egg infection assays were used to evaluate the biofilm-forming activity of DST659 and DST693 genotypes. Medical records of the patients infected by these two genotypes were retrospectively reviewed. High biofilm-forming activity of DST659 isolates was demonstrated in vitro and further proved with the zebrafish egg infection model, which showed a positive correlation between the biofilm-forming extent on chorion and the in vitro biofilm activity. Moreover, significantly less embryos survived when infected with DST659 isolates than those with DST693 (1.25% vs. 11.43%), and the high-biofilm subset of DST659 showed a greater reduction in survival of embryos at 48 h post-infection than the low-biofilm subset (0 vs. 1.92%). Patients infected with DST659 seemed to survive slightly worse than those infected with DST693, although the difference was insignificant. It is noteworthy that DST659-infected patients were associated with a higher incidence in renal insufficiency as compared to those with DST693, the low biofilm genotype. We suggest that a strong biofilm activity of DST659 contributed to a high mortality rate in zebrafish hosts and poor renal function in patients, as well as gaining the dominance in the northern Taiwan.