<b>Bacterial microflora in the gastrointestinal tract of Nile tilapia, <em>Oreochromis niloticus</em>, cultured in a semi-intensive system</b>- DOI: 10.4025/actascibiolsci.v25i2.2007

Abstract

This experiment measured total bacterial numbers in the gastrointestinal regions of semi-intensively cultured tilapia, Oreochromis niloticus L. (Cichlidae). Mean bacterial numbers were higher in both anterior and posterior gut than in stomach. The percentage of isolated species and the percentage of isolates from any particular species varied significantly among gastrointestinal tract regions. Aeromonas hydrophila, Aeromonas veronii, Burkholderia cepacia, Chromobacterium violaceum, Citrobacter freundii, Escherichia coli, Flavimonas oryzihabitans and Plesiomonas shigelloides were the most frequently isolated Gram-negative bacilli. From these samples, only Plesiomonas shigelloides was present in both gastrointestinal regions, with higher number in the posterior gut (76%), when compared to anterior gut (4.8%) and stomach (0.6%). Aeromonas hydrophila (0.6%), Escherichia coli (7.4%), and Flavimonas oryzihabitans were isolated only in the stomach, and Citrobacter freundii and Burkholderia cepacia were found only in the posterior gut. Chromobacterium violaceum was the dominant bacteria isolated from stomach and anterior gut, with 90% and 55%, respectively. Unidentified organisms comprised 0 - 39.3% of the gastrointestinal microflora