Efficacy of in-feed probiotics vs. skin infections for the rainbow trout.

A review of: Pieters, N., Brunt, J., Austin, B., & Lyndon, a R. (2008). Efficacy of in-feed probiotics against Aeromonas bestiarum and Ichthyophthirius multifiliis skin infections in rainbow trout (Oncorhynchus mykiss, Walbaum). Journal of applied microbiology, 105(3), 723-32.

Aquaculture has been a rapidly growing industry for a few decades now and there have been some problems involved with growing fish outside of their natural habitat. Disease, parasites and welfare/ stress of the fish have been common issues within aquaculture and the introduction of probiotics has helped to relieve the pressures of some individual cases as shown by Ferguson et al, (2010), where his investigation found that oral supplementation of Pediococcus acidilactici stimulated some aspects of immune response of the red tilapia (Oreochromis niloticus).

In this study the authors investigated the efficacy of in-feed probiotics against skin infections caused by Aeromonas bestiarum (A. bestiarum) and Ichthyophthirius multifiliis (Ich) in the rainbow trout (Oncorhynchus mykiss, Walbaum). They did this by inducing both of the skin infections by intradermal injections directly into the dorsal fin base, each of the probiotics were administered orally (108 cells per g feed for GC2 [Aeromonas sobria] and 1010 cells per g feed for BA211 [Brochothrix thermosphacta]) for two weeks. At the end of the feed trial the trout were dissected aseptically and blood and kidney samples were taken. The authors then counted blood cells and used several assays to look at the pinocytic, chemotactic, alternative complement pathway (ACP), serum lysozyme and epidermal mucus lysozyme activities the authors also looked into intracellular respiratory burst assay and Epidermal mucus total protein concentration.

The results showed for skin infection A. bestiarum probiotic GC2 led to 76% survival and BA211 led to 88% survival compared to the control which only had a 22% survival rate. For the infection Ich the probiotic GC2 led to 100% survival BA211 led to 2% survival and the controls had a survival rate of 0%. The analysis of innate immune responses showed that probiotic GC2 resulted in higher phagocytic activity, whereas probiotic BA211 showed enhanced respiratory burst activity.

The authors conclude that GC2 was the more effective probiotic although both probiotics stimulated different pathways in the innate immune response system. This study is of great significance as it was the first to show that probiotics could be used to treat epidermal skin infections which can be applied in aquaculture of rainbow trout.

Reference: Ferguson, R. M. W., Merrifield, D. L., Harper, G. M., Rawling, M. D., Mustafa, S., Picchietti, S., Balcázar, J. L., et al. (2010). The effect of Pediococcus acidilactici on the gut microbiota and immune status of on-growing red tilapia (Oreochromis niloticus). Journal of applied microbiology, 109(3), 851-62.