Prevalence of bacterial pathogens and their anti-microbial resistance in Tilapia and their pond water in Trinidad.

ABSTRACT

In Trinidad, Tilapia (Oreonchromis spp.) is one of the most important fresh water food fish and the number of farms has been increasing annually. A study was conducted in the local tilapia industry to determine the microbial quality of pond water, prevalence of bacterial pathogens and their anti-microbial resistance using the disk diffusion method. Seventy-five apparently healthy fish and 15 pond water samples from three of the four commercial tilapia fish farms in the country were processed. The 202 bacterial isolates recovered from fish slurry and 88 from water, belonged to 13 and 16 genera respectively. The predominant bacteria from fish slurry were Pseudomonas spp. (60.0 per cent), Aeromonas spp. (44.0 per cent), Plesiomonas (41.3 per cent) and Chromobacterium (36.0 per cent) (P < 0.05; chi(2)) compared with isolates from pond water where Bacillus spp. (80.0 per cent), Staphylococcus spp., Alcaligenes spp. and Aeromonas spp. (60.0 per cent) were most prevalent (P < 0.05; chi(2)). Using eight anti-microbial agents, to test bacteria from five genera (Aeromonas, Chromobacterium, Enterobacter, Plesiomonas and Pseudomonas), 168 (97.1 per cent) of 173 bacterial isolates from fish slurry exhibited resistance to one or more anti-microbial agents compared with 47 (90.4 per cent) of 52 from water (P > 0.05; chi(2)). Resistance was high to ampicillin, 90.2 per cent (158 of 173), erythromycin, 66.5 per cent (115 of 173) and oxytetracycline, 52.6 per cent, (91 of 173) but relatively low to chloramphenicol, 9.8 per cent (17 of 173) and sulphamethoxazole/trimethoprim, 6.4 per cent (11 of 173) (P < 0.05; chi(2)). For pond water isolates, the frequency of resistance across bacterial genera ranged from 75 per cent (nine of 12) for Chromobacter spp. to 100 per cent found amongst Enterobacter spp. (six of six), Plesiomonas spp. (nine of nine) and Pseudomonas spp. (eight of eight) (P < 0.05; chi(2))...