Seasonal variation in the intestinal bacterial flora of hybrid tilapia (Oreochromis niloticus x Oreochromis aureus) cultured in earthen ponds in Saudi Arabia

Seasonal quantitative and qualitative analyses of the bacterial flora associated with the intestine of hybrid tilapia (Oreochromis niloticus X Oreochromis aureus) cultured in earthen ponds in Saudi Arabia were carried out. The isolates were being identified to genus or species level. Total viable counts (TVC) of bacteria in the intestine varied between 6.8 +/- 1.9 x 10(6) to 7.5 +/- 1.4 x 10(7) Colony forming units (cfu) g(-1) in early summer, 1.6 +/- 2.0 x 10(6) to 5.1 +/- 2.5 x 10(7) cfu g(-1) in summer, 3.1 +/- 1.4 x 10(8) to 1.3 +/- 2.2 x 10(9) cfu g(-1) in autumn, and 8.9 +/- 1.8 x 10(5) to 1.3 +/- 0.9 x 10(7) cfu g(-1) in winter. Altogether, 17 bacterial genera were identified from the intestine of tilapia. The bacteria were predominantly Gram-negative rods (77%). Aeromonas hydrophila, Shewanella putrefaciens, Corynebacterium urealyticum, Escherichia coli and Vibrio cholerae were the most abundant species with a prevalence of > 10% in most cases except V cholerae. Considerable numbers of Pseudomonas spp. were found only in winter. Photobacterium damselae, Pasteurella spp., Cellulomonus sp. and Bacillus sp. were present in some seasons of the year. (C) 2004 Elsevier Science B.V. All rights reserved.