Cadmium tolerance and antibiotic resistance of Pseudomonas sp. isolated from water, sludge and fish raised in wastewater-fed tropical ponds.

ABSTRACT

The numbers of Pseudomonas sp. isolated were counted in samples collected from water, sludge and intestine of fishes raised in different wastewater ponds along an effluent gradient in a sewage treatment plant. Total fish yield in the last maturation pond increased by 73% over the yield in first maturation pond or facultative pond. The number of Pseudomonas sp. isolated from the intestine of the tilapia (Oreochromis mssambicus) raised in facultative pond, was more than three times the counts (7.22 x 10(8)/g) observed in the last maturation pond (2.025 x 10(8)/g). The effective lethal concentration of cadmium for Pseudomonas sp. isolated from the intestine of the tilapia was 0.6 mM and 0.08-0.09 mM when the fish was procured from facultative pond and last maturation pond, respectively. The Pseudomonas sp. isolated from the intestine of the tilapia did not have resistance to any of the ten antibiotics tested. However, the bacterium isolated from raw sewage, water and sediment of the anaerobic pond was resistant to seven out of ten antibiotics tested.