Isolation of Potentially Pathogenic Bacterial Flora from Tropical Sea Urchins in Selected West Atlantic and East Pacific Sites

Microbiologic studies of healthy echinoids from sites in the tropical West Atlantic and East Pacific Oceans, were undertaken. Tissues obtained from suspected diseased populations of Diadema antillarum in the Key West, Florida area also were cultured. A total of 199 environmental bacterial isolates (both aerobic and anaerobic) were cultivated from Aristotle's lantern, gut and gonadal tissues of specimens of Diadema antillarum, D. mexicanum, D. paucispinum, Echinometra lucunter, E. mathaei, Lytechinus variegatus and Tripneustes ventricosus. The largest number were cultured from the gut, while much smaller bacterial populations were obtained from the lantern and gonads. The composition of the bacterial communities appears to consist primarily of the endospore-forming, toxin-producing, Gram-positive bacilli Bacillus and Clostridium, with clostridial isolates dominating the bacterial microtlora of the gut. This finding contrasts with earlier reports that strains of Vibrio are the major colonizers of the gastrointestinal tract in Echinus esculentus as well as other marine invertebrates. The aeromonads and vibrios were the predominant Gram-negative isolates with pseudomonads and flavobacteria next in abundance. Enterobacter, Enterococcus, Flavimonas, Streptococcus, Bacteroides and Serratia were less frequently isolated genera.