Quantitative and qualitative bacterial flora of giant freshwater prawn Macrobrachium rosenbergii cultured in earthen ponds in Saudi Arabia

Quantitative and qualitative analyses of bacterial flora associated with the digestive tract of the giant freshwater prawn Macrobrachium rosenbergii cultured in earthen ponds of Saudi Arabia were carried out. Bacterial counts and flora of prawn-culture pond water. sediment, and prawn carapaces, along with important physicochemical parameters, were investigated, and the isolates were identified to the genus or species level. Total viable counts (TV( : mean +/- SD) varied between (1.0 +/- 2.3) X 10(4) and (1.7 +/- 0.8) X 10(5) colony-forming units (cfu) per milliliter in pond water, (5.8 +/- 1.7) X 10(7) and (1.1 +/- 2.9) X 10(9) efu/g in sediment, ( 1.5 +/- 0.9) X 10(5) and (1.6 +/- 2.4) X 10(6) cfu/cm(2) in the carapace, and (9.1 +/- 1.5) X 10(6) and (8.7 +/- 1.8) X 10(7) efu/g in the digestive tract of freshwater prawns. The bacterial flora was predominantly gram-negative, accounting for 80% of total isolated strains. Altogether, 21 bacterial species of 16 genera were identified. Aeromonas hydrophila, Shewanella putrefaciens, other Aeromonas spp.. Vibrio spp., and Enterococcus spp. were the most abundant bacterial species (prevalence >= 10%) in pond water; A. hydrophila, S. putrefaciens, Vibrio spp., and Pseudomonas spp. were the most abundant in sediment: S. putrefaciens, A. hydrophila, Vibrio spp., Enterocuccus spp,. and Aeromonas spp. were the most abundant on the prawn carapace; and A. hydrophila. S. putrefaciens. Vibrio spp.. Enterococcus spp., and Pasteurella spp. were the most abundant in the digestive tracts. In every population studied, Aeromonas spp., S. putrefaciens, Enterococcus spp.. Vibrio spp.. Pasteurella spp., Chryseomonas spp., and Pseudomonas spp. were present.