Inhibiting the causative agent of snake fungal disease, Ophidiomyces ophiodiicola, with common cutaneous bacteria isolated from snake skin.

Abstract

Recent declines of North American snake populations have increased conservation concerns. These declines have been attributed in part to snake fungal disease (SFD) caused by mycotic infection of Ophidiomyces ophiodiicola (Oo). Multicellular organisms, including reptiles, have a beneficial microbial assemblage on their skin that defend the host from disease. We hypothesized that the snake skin microbiome may protect its host against SFD by production of antifungal metabolites, outcompeting Oo for space, and/or stabilizing the microbial community possibly increasing innate defensive immunity. The objectives of this project were to 1) obtain culturable resident bacterial isolates from snake skin, 2) genotype culturable isolates, and 3) challenge all isolates against Oo to determine if antifungal activity is present in the host microbiome which may translate to an innate protective response against SFD. From the twelve captured snakes, four black racers (Coluber constrictor) and eight timber rattlesnakes (Crotalus horridus), microbial samples were collected using a standardized swabbing technique. Those swabs from the 12 host snakes yielded a total of 58 bacterial colonies that were isolated, genotyped, and challenged against Oo. Sixteen of these bacterial isolates inhibited the growth of Oo in vitro. Species of antifungal bacteria occurred in the genera Aeromonas, Erwinia, Myroides, Morganella, and Stenotrophomonas, along with in the families Bacillaceae and Enterobacteriaceae. This study sheds light on the innate immune function of the culturable snake cutaneous microbiome and the resident probiotic members which may play a vital part in the fight against this emergent disease for both infected and uninfected hosts.