Fig. 5

Candida parapsilosis cell-free culture fraction protects zebrafish from infection by Candida albicans. (A) Schematic of infection model. The larval zebrafish swimbladder offers a transparent vertebrate mucosal infection model that is amenable to non-invasive imaging of both the host and the pathogen. (B–D) Zebrafish at 4 days post-fertilization with inflated swimbladders were infected in their swimbladders by glass needle injection with C. albicans yeast cells (C.a.) suspended in control (H4) media or in supernatants from C. parapsilosis (C.p. Supt) or C. albicans (C.a. Supt.) cultures. (B) Relative survival of fish infected with C. albicans with or without Candida supernatants. All C. albicans-infected fish cohorts are significantly different from their respective controls. C. parapsilosis supernatants significantly reduce the mortality of a C. albicans infection (denoted by γ). Matching Greek letters label individual comparisons: α, p < 0.01; β, p < 0.0001; γ, p < 0.05. Survival data are pooled from two independent experiments, n = 20 per group. All pair-wise comparisons were made with the Mantel–Cox test. (C,D) Fish from the experiment in (B) were viewed by fluorescence microscopy at 24 h post-infection and scored for two indicators of infection, swimbladder deflation [(C) **p < 0.01] and breaching of epithelial barrier (D). Examples of these phenotypes are shown in Figure S1 in Supplementary Material. Data were pooled from two independent experiments and analyzed by Fisher’s exact test with Bonferroni correction (Control media, n = 22, C.a. supernatant, n = 21, C.p. supernatant, n = 22).