Faecal coliforms in pond water, sediments and hybrid tilapia <i>Oreochromis niloticus</i>×<i>Oreochromis aureus</i> in Saudi Arabia

Abstract

Total bacterial load, total coliforms faecal coliforms in pond water, sediment, intestine of hybrid tilapia Oreochromis niloticus×Oreochromis aureus and pigeon Columba livia faeces were investigated monthly over a period of 1 year from July 1999 to June 2000. Fish were collected randomly by a cast net. Samples were analysed for coliforms using the multiple-tube fermentation technique. Results showed total viable bacterial counts in the pond water, sediment, intestine of tilapia and pigeon faeces ranging from 1.8±0.9×102 to 6.0±1.2×104 cfu mL−1, 3.2±1.2×105 to 2.8±1.5×107 cfu g−1, 8.2±1.6×105 to 9.9±1.5×107 cfu g−11.0±0.4×107to9.7±0.2×109 cfu g−1respectively. The most probable number (MPN) of coliforms and faecal coliforms ranged from 287±12 to ≥1600±0 100 mL−1 in pond water; the MPN ranges for sediment, tilapia intestine and pigeon faeces were 257±29 to ≥1100±0 g−1, 237±46 to ≥1100±0 g−1 and 403±98 to ≥1100±0 g−1 respectively. The abundance of normal bacteria coliforms was greater in the warm months than in the cold months. Ground water was free from any sort of coliform organisms, and there were no sources of human faecal matter in the pond. So, it is clear that faecal coliforms from pigeon faeces significantly contaminated (P<0.05) the ponds and tilapia intestines. Escherichia coli was the only coliform organism found in pond water, sediment, intestine of tilapia and pigeon faeces.