IN VITRO INHIBITION OF SHELL FLORA BY A COMMERCIAL PROBIOTIC MARKETED FOR USE IN CAPTIVE HERMIT CRABS (COENOBITA SPP.)

Captive hermit crabs (Coenobita spp.) are wild-caught and sold wholesale by commercial distributors. Probiotic products that are marketed for use in captive hermit crabs are commercially available. These products do not disclose the cultures present nor how they may affect hermit crab health. The objectives of this study were to identify culturable organisms present in one such probiotic product and to investigate their interaction in vitro with microbial isolates from the shells and exoskeletons of clinically healthy captive hermit crabs. Samples from two lots of a commercial probiotic product and swabs from seven captive hermit crabs were cultured under aerobic conditions at ambient temperature on standard media. From the resulting colonies, morphologically distinct bacterial cultures were identified using matrix-assisted laser desorption ionization time-of-flight (MALDI-tof) mass spectrometry or commercial biochemical analysis. Bacillus pumilus and Bacillus licheniformis were identified from the probiotics via MALDI-tof mass spectrometry. Each shell flora isolate was plated uniformly on blood agar along with B. pumilus and B. licheniformis, respectively. B. pumilus inhibited the growth of other Bacillus species and all Gram-negative species described. This investigation demonstrates that organisms isolated from a commercial probiotic have in vitro inhibitory effects on select shell flora isolated from captive hermit crabs. Commercial probiotics may be useful for the husbandry of captive hermit crabs, but further studies are required to demonstrate clinical efficacy against disease.