Microbial quality of oysters sold in Western Trinidad and potential health risk 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 oyster cocktails sampled from 72 vendors across Western Trinidad were determined. The microbial quality of the water used in the preparation of raw oysters was also investigated. Of 200 samples each of raw oysters, condiments/spices and oyster cocktails tested, 154 (77.0 percent), 89 (44.5 percent) and 154 (77.0 percent) respectively yielded E. coli. The differences were statistically significant (P= <0.001; chi square = 62.91). The mean E. coli count 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 hundred and forty six (73.0 percent) oyster cocktails contaminated with E. coli had counts that exceeded the recommended standard of 16 per g. Of a total of 590 E. coli isolates from various sources tested, 24 (4.1 percent0, 20 (3.4 percent) and 69 (11.7 percent) were mucoid, haemolytic and non-sorbitol fermenters respectively. Twelve (2.0 percent) isolates of E. coli were O157 strains, while 92 (46.0 percent) of 200 E.coli isolates tested belonged to enteropathogenic serogroups. Ninety (45.0 percent) and 73 (36.5 percent) of 200 water samples contained total coliforms and faecal coliforms respectively, with counts that exceeded 2.2 coliforms per 100 ml. Salmonella spp. were isolated from 7 (3.5 percent), 1 (0.5 percent) and 2 (1.0 percent) of 200 samples each, of raw oysters, condiments/spices and oyster cocktails respectively. Oysters pose a health risk to consumers in Trinidad, particularly from colibacillosis and salmonellosis, and the need for increased public awareness of this hazard cannot be over-emphasized. (AU)

Public health aspects of halophilic vibrios in Jamaica

The occurrence of bacteria in oysters (Crassotrea rhizophorae) and seawater from Jamaican commercial oyster-culture sites was determined, using standard microbiological methods. Vibrio vulnificus, V. cholerae (non-01, non-toxigenic), V. parahaemolyticus and V. alginolyticus were identified in seawater samples, and the latter two mildly pathogenic species in oysters. The pathogenicity of halophilic vibrios is reviewed. The results suggest that correct selection of oyster-culture sites may significantly reduce the public health hazards associated with shellfish, and that more and precise information is required on the geographical and seasonal distribution of infection risk (AU)