Listeria monocytogenes in Milk Products

peer-reviewedMilk and milk products are frequently identified as vectors for transmission of Listeria monocytogenes. Milk can be contaminated at farm level either by indirect external contamination from the farm environment or less frequently by direct contamination of the milk from infection in the animal. Pasteurisation of milk will kill L. monocytogenes, but post-pasteurisation contamination, consumption of unpasteurised milk and manufacture of unpasteurised milk products can lead to milk being the cause of outbreaks of listeriosis. Therefore, there is a concern that L. monocytogenes in milk could lead to a public health risk. To protect against this risk, there is a need for awareness surrounding the issues, hygienic practices to reduce the risk and adequate sampling and analysis to verify that the risk is controlled. This review will highlight the issues surrounding L. monocytogenes in milk and milk products, including possible control measures. It will therefore create awareness about L. monocytogenes, contributing to protection of public health

Incidence of Vibrio parahaemolyticus in raw fish, oysters, and shrimp [Incidencia de Vibrio parahaemolyticus en pescado, ostión y camarón crudos.]

The incidence of Vibrio parahaemolyticus in fresh seafood sold in Guadalajara, was studied by two procedures. These two procedures were compared to choose a reliable technique when outbreaks of V. parahaemolyticus illness occur. For one year, 57 samples of fresh oysters, fish and shrimp were analyzed for mesophilic aerobic bacteria (MAB) content, V. parahaemolyticus and pH. Total volatile nitrogen (TVN) was also determined in samples of fish and shrimp. MAB were counted by the pour plate method, and TVN was determined by modified Conway's micro diffusion technique. V. parahaemolyticus was investigated in 20-g samples by enrichment in lauryl dextrose salt broth (LDSB), isolating on plates of thiosulfate citrate bile sucrose agar (TCBS) and bile salts No. 3 agar (BS No. 3), and by direct isolation on TCBS and BS No.3 agar plates. Vibrio was characterized by tests described in standard methods, based upon the halophilism of the organism. Global percent of Vibrio parahaemolyticus positive samples was 45.6%, being 71.4% in fish, 44.0% in oysters, and 27.6% in shrimp. The use of two techniques enhanced the ability to recover the vibrio. There was a greater number of positives during the warm months (p = 0.0038). Means of TVN and pH in both positive and negative samples were not significantly different. Means of MAB counts were similar either in positive or negative samples

[Incidence of Vibrio parahaemolyticus in raw fish, oysters, and shrimp]

The incidence of Vibrio parahaemolyticus in fresh seafood sold in Guadalajara, was studied by two procedures. These two procedures were compared to choose a reliable technique when outbreaks of V. parahaemolyticus illness occur. For one year, 57 samples of fresh oysters, fish and shrimp were analyzed for mesophilic aerobic bacteria (MAB) content, V. parahaemolyticus and pH. Total volatile nitrogen (TVN) was also determined in samples of fish and shrimp. MAB were counted by the pour plate method, and TVN was determined by modified Conway's micro diffusion technique. V. parahaemolyticus was investigated in 20-g samples by enrichment in lauryl dextrose salt broth (LDSB), isolating on plates of thiosulfate citrate bile sucrose agar (TCBS) and bile salts No. 3 agar (BS No. 3), and by direct isolation on TCBS and BS No.3 agar plates. Vibrio was characterized by tests described in standard methods, based upon the halophilism of the organism. Global percent of Vibrio parahaemolyticus positive samples was 45.6%, being 71.4% in fish, 44.0% in oysters, and 27.6% in shrimp. The use of two techniques enhanced the ability to recover the vibrio. There was a greater number of positives during the warm months (p = 0.0038). Means of TVN and pH in both positive and negative samples were not significantly different. Means of MAB counts were similar either in positive or negative samples

Incidence of Vibrio parahaemolyticus in raw fish, oysters, and shrimp [Incidencia de Vibrio parahaemolyticus en pescado, osti�n y camar�n crudos.]

The incidence of Vibrio parahaemolyticus in fresh seafood sold in Guadalajara, was studied by two procedures. These two procedures were compared to choose a reliable technique when outbreaks of V. parahaemolyticus illness occur. For one year, 57 samples of fresh oysters, fish and shrimp were analyzed for mesophilic aerobic bacteria (MAB) content, V. parahaemolyticus and pH. Total volatile nitrogen (TVN) was also determined in samples of fish and shrimp. MAB were counted by the pour plate method, and TVN was determined by modified Conway's micro diffusion technique. V. parahaemolyticus was investigated in 20-g samples by enrichment in lauryl dextrose salt broth (LDSB), isolating on plates of thiosulfate citrate bile sucrose agar (TCBS) and bile salts No. 3 agar (BS No. 3), and by direct isolation on TCBS and BS No.3 agar plates. Vibrio was characterized by tests described in standard methods, based upon the halophilism of the organism. Global percent of Vibrio parahaemolyticus positive samples was 45.6%, being 71.4% in fish, 44.0% in oysters, and 27.6% in shrimp. The use of two techniques enhanced the ability to recover the vibrio. There was a greater number of positives during the warm months (p = 0.0038). Means of TVN and pH in both positive and negative samples were not significantly different. Means of MAB counts were similar either in positive or negative samples

Risk of salmonellosis associated with consumption of chocolate in mexico

To assess the potential risk of salmonellosis associated with consumption of chocolate, the prevalence of Salmonella spp. was investigated in retail wrapped and nonwrapped solid chocolate in Guadalajara, Mexico. Previously, the efficiency of preenrichment and enrichment methods to isolate low numbers of Salmonella in chocolate was compared. Though not completely efficient, a preenrichment in nonfat milk without brilliant green, followed by enrichment in tetrathionate and selenite cystine broths gave better results than the other methods studied. Regarding the survey of retail chocolate, Salmonella was isolated from 2 (4.5%) of 44 samples of wrapped chocolate and from none of 56 samples of nonwrapped chocolate. The serovars identified were Salmonella agona and Salmonella derby. There were no significant differences between coliform counts or total bacterial counts obtained from wrapped and nonwrapped chocolate. The presence of Salmonella in chocolate is of concern due to the several low-infectivedose Salmonella outbreaks that have been linked to chocolate. On the other hand, a technique capable of detecting low numbers of Salmonella in chocolate is still needed. Copyright �, International Association of Milk, Food and Environmental Sanitarians