Pathogenic bacteria associated with oysters (Crassostrea brasiliana) and estuarine water along the south coast of Brazil.

Oysters and estuarine water samples were collected monthly, from June 1998 to March 1999, in the Cananéia estuary, on the south coast of São Paulo, Brazil, and analyzed for bacterial hazards with and without depuration in filtered estuarine water. Aeromonas spp., Plesiomonas shigelloides, Vibrio cholerae O1, Vibrio parahaemolyticus, and Vibrio vulnificus were counted in oyster samples using the most probable number (MPN) and their presence verified in the surrounding estuarine water samples. The presence of Salmonella, Shigella, Escherichia coli O157:H7, and fecal coliforms counts were determined in oysters and in water samples too. Sixty percent of water samples contained fecal coliforms ranging from <1 to >200 CFU/100 ml and 100%, 30%, 20% and 10% were positive for V. parahaemolyticus, Salmonella, Aeromonas, and V. vulnificus in 5 l of water samples, respectively. In oyster samples, the fecal coliforms concentration ranged from <3.0 to > or =2.4 x 10(3) MPN/g in 40% of untreated and from <3.0 to 1.1 x 10(3) MPN/g in 40% of treated samples. Vibrio parahaemolyticus Kanagawa-negative was detected in all oyster samples and their concentration varied from 3.6 to > or =2.4 x 10(3) MPN/g. For the untreated oyster samples 80%, 70%, and 10% were positive for V. vulnificus (<3 - 11.0 MPN/g), Aeromonas (<3-15 MPN/g), and Salmonella (presence in 25 g), respectively. However, for treated oyster samples 60%, 30%, and 0% of them contained the same bacteria, respectively. Escherichia coli O157:H7, Shigella spp., P. shigelloides, and V. cholerae O1 were not detected in any of the samples. Fecal indicators did not correlate with Vibrio presence (p>0.05), although the isolation of Aeromonas species had a positive correlation (p = 0.017). The results showed no correlation between temperature, salinity, and bacteria (p > 0.05). The comparison between bacterial concentration in treated and untreated oyster samples, showed that only Aeromonas was higher in untreated oyster samples (p = 0.039). This study contributes toward creating a more global understanding of food-borne bacterial pathogens. The presence and concentration of viable bacterial hazards in oysters and water surrounding areas was determined for the first time on the south coast of São Paulo and it helps to define better the true microbial hazard in the aquatic environment and oysters.

An Improved Enrichment Procedure for the Isolation of Yersinia enterocolitica and Related Species From Milk.

A new enrichment procedure is proposed to improve the isolation of Yersinia enterocolitica and related species from milk. This procedure uses tryptic soy broth plus Polymyxin (5 IU/ml) and Novobiocin (10 µg/ml) - TSPN broth - incubated at 18°C for 3 d. Using raw milk and pasteurized milk inoculated with Yersinia strains, the efficiency of this procedure was compared to that of SB broth (sorbitol bile salts broth) incubated at 4°C for up to 21 d. Despite of the presence of antibiotics in TSPN broth, there were difficulties in recovering Yersinia from raw milk samples due to the presence of high levels of other organisms. Nevertheless, TSPN broth incubated at 18°C for 3 d showed better efficiency than the other method. In pasteurized milk samples, TSPN medium at 18°C for 3 d gave better results than the SB broth at 4°C for 7 d, showing that the proposed procedure is the preferable one due to the shorter period of incubation.