Edwardsiella tarda isolated in integrated fish farming

摘要

The use of pig manure in fish farming reduces the environmental pollution from this material and gives it an economic application. However, the microbioloical implications of such a process are not completely understood. Five hundred and forty tilapia Oreochromis niloticus L. from an integrated fish farm (using pig excrements as food) were collected and evaluated microbiologically for the presence of Edwardsiella tarda. Samples of the external surface (skin, gills and fin), intestines and muscle were analysed. E. tarda was isolated from 93 (17.2%) of the external surface samples, 77 (14.3%) of the muscle samples and 61 (11.2%) of the intestine samples. These rates were compared using the chisquared test, which showed that the skin samples had higher contamination than the others. Selenitecystine (SC) broth was better than Rappaport-Vassiliadis (RV) enrichment broth for the microbiological assay. Salmonella-Shigella (SS) agar presented superior performance to that of Hektoen enteric (HE) medium. The combination SC and SS showed the best efficiency for E. tarda detection, isolating the bacterium in 107 (6.6%) out of 1620 samples studied.