In vitro activity of lactoferricin solution against Malassezia pachydermatis from otitis externa in dogs and cats

Background Malassezia pachydermatis is a commensal organism of the skin, yet it may induce dermatitis and/or otitis. Lactoferricin (Lfcin) is an antimicrobial peptide obtained by the pepsin‐mediated digestion of lactoferrin, a multifunctional innate‐defence milk protein. The antibacterial activity of Lfcin is thought to cause alteration of bacterial membrane permeability, thus inducing cell death. Objectives The aim of this study was to evaluate in vitro antifungal activity of different dilutions of Lfcin solution against M. pachydermatis strains isolated from ears of dogs and cats with otitis externa. Methods and materials Fifty clinical Malassezia isolates from 40 dogs and 10 cats were tested. A dilution method in microtitre plates was used starting with a 20% Lfcin water solution. The different dilutions were 2:1 (13.3%), 1:1 (10%), 1:2 (6.7%), 1:5 (3.3%) and 1:10 (1.8%). Results were expressed as the value at which the growth of 50% (minimal fungicidal concentration MFC50) and 90% (MFC90) of yeast cells was inhibited. Results All strains showed susceptibility to 20% Lfcin solution (100%). With 1:5 and 1:10 dilutions corresponding to 3.3% and 1.8% Lfcin solutions, all strains showed resistance. The MFC50 and MFC90 values were observed at 13.3% and 20% Lfcin solutions. Conclusions and clinical relevance The results indicated that Lfcin solution exhibits the antimicrobial activity specific to antimicrobial peptides. In particular, the 20% solution can be effective in killing M. pachydermatis isolated strains. Some susceptibilities also are evident at lower concentrations of ≤6.7% for four strains. Résumé Contexte Malassezia pachydermatis est un organisme commensal de la peau pouvant induire une dermatite et/ou une otite à Malassezia. La lactoferricine (Lfcin) est un peptide antimicrobien obtenu par la digestion de la lactoferrine, médiée par la pepsine, une protéine du lait multifonctionnelle de la défense innée. On pense que l’activité antibactérienne de Lfcin cause une altération de la perméabilité membranaire induisant ainsi la mort cellulaire. Objectifs Le but de cette étude était d’évaluer l’activité antifongique in vitro de différentes dilutions de solution de Lfcin contre les souches de M. pachydermatis isolées des oreilles des chiens et des chats avec otite externe. Matériels et méthodes Cinquante souches cliniques de Malassezia isolées de 40 chiens et 10 chats ont été testées. Une méthode de dilution dans les plateaux de microtitre a été utilisée