Experimental biofilm-related Candida infections.

Aim: We investigated the pathogenic role of biofilm and the therapeutic efficacy of anidulafungin in experimental infections of the wax moth Galleria mellonella by Candida albicans clinical strains.

Materials & Methods: On the basis of the in vitro propensity to form biofilm, five biofilm-producer (BP) and four nonproducer (NP) C. albicans clinical strains were used in this study. For each strain, we assessed the virulence by infecting G. mellonella larvae and observing survival. Anidulafungin was administered 2 h after yeast inoculum at 0.6 µg, according to the therapeutic dose recommended for humans.

Results: Biofilm-forming ability highly influenced the larva-killing rate. A significant (p < 0.0001) survival decrease was observed in the BP group, with 80% of the infected larvae dying within 72 h. NP isolates did not reach the same killing rate, even at the end of experiments (216 h). Larval survival was enhanced (p < 0.0001) by anidulafungin administration in both groups. Survival rate at 72 h was similar in both groups (BP 78.5% and NP 87.5%); whereas there were still differences at the end of the experiments, with a higher survival in the NP group (75 vs 48%).

Conclusion: Our data confirm the pathogenic role of biofilm in C. albicans infections. Its importance was further enhanced by a lack of contribution from extracellular enzymes, detected in both NP and BP strains. In addition, we demonstrated anidulafungin efficacy in treating biofilm-related invasive candidiasis.