FC‐5 Unsaturated transferrin inhibits the growth of Malassezia pachydermatis in vitro

Abstract

Transferrin, an iron‐binding protein that transports iron to mammalian cells, may contribute to innate immunity to fungal pathogens, primarily by limiting microbial access to iron. We investigated whether unsaturated (apo)‐transferrin had an inhibitory effect in vitro on Malassezia pachydermatis, an important opportunistic cutaneous yeast pathogen of dogs. M. pachydermatis strains were grown at 32°C in medium containing canine or bovine apo‐transferrin at concentrations of 0.7, 1.3, 2.7 and 5.3 mg/mL. Optical density (OD492) was measured daily until growth was stationary (day 6) in saline‐control wells and then compared between treatments by ANOVA and Tukey's tests. Bovine and canine transferrin inhibited (P < 0.01) yeast growth at all concentrations tested. Using bovine transferrin, the mean OD ± SE for 10 strains were: saline, 0.55 ± 0.19; 0.7 mg/mL, 0.33 ± 0.05; 1.3 mg/mL, 0.18 ± 0.03; 2.7 mg/mL, 0.18 ± 0.04; 5.3 mg/mL, 0.16 ± 0.03. Using canine transferrin, the mean OD ± SE for seven strains were: saline, 0.79 ± 0.03; 0.7 mg/mL, 0.37 ± 0.07; 1.3 mg/mL, 0.27 ± 0.04; 2.7 mg/mL, 0.24 ± 0.03; 5.3 mg/mL, 0.20 ± 0.03. For both bovine and canine transferrin, inhibition by 5.3 mg/mL exceeded (P < 0.05) that of 0.7 mg/mL. Since both bovine and canine apo‐transferrin inhibit the growth of M. pachydermatis in vitro, serum transferrin may contribute to innate immunity to M. pachydermatis indogs and cattle. The spongiotic dermatitis reaction seen histologically in many dogs with Malassezia dermatitis may promote the accumulation of transferrin at infection sites. Funding: Self‐funded.