Microbial quality of oysters sold in Western Trinidad and potential healthrisk to consumers

The prevalence and characteristics of Escherichia coli and Salmonella spp. as well as counts of E. coli in raw oysters, condiments/spices, and raw oys ter cocktails sampled from 72 vendors across Western Trinidad were determin ed. The microbial quality of the water used in the preparation of raw oyste rs was also investigated. Of 200 samples each of raw oysters, condiments/sp ices and oyster cocktails tested, 154 (77.0 %), 89 (44.5 %) and 154 (77.0 % ) respectively yielded E. coli. The differences were statistically signific ant (P = less than or equal to 0.001; chi(2) = 62.91). The mean E. coli cou nt per g in the ready-to-eat oyster cocktail ranged from 1.5 x 10(3) +/- 2. 7 x 10(3) in Couva to 8.7 x 10(6) +/- 4.9 x 10(7) in San Fernando. One hund red and forty-six (73.0 %) oyster cocktails contaminated with E. coli had c ounts that exceeded the recommended standard of 16 per g. Of a total of 590 E. coli isolates from various sources tested, 24 (4.1 %), 20 (3.4 %) and 6 9 (11.7 %) were mucoid, haemolytic and non-sorbitol fermenters respectively . Twelve (2.0 %) isolates of E. coli were O157 strains, while 92 (46.0 %) o f 200 E. coli isolates tested belonged to enteropathogenic serogroups. Nine ty (45.0 %) and 73 (36.5 %) of 200 water samples contained total coliforms and faecal coliforms respectively, with counts that exceeded 2.2 coliforms per 100 mi. Salmonella spp. were isolated from 7 (3.5 %), 1 (0.5 %) and 2 ( 1.0 %) of 200 samples each, of raw oysters, condiments/spices and oyster co cktails respectively. Oysters pose a health risk to consumers in Trinidad, particularly from colibacillosis and salmonellosis, and the need for increa sed public awareness of this hazard cannot be over-emphasized.