ABSTRACT
Selenite-cystine/trimethylamine oxide/dulcitol medium has been used in conjunction with conductance instruments to detect the presence of Salmonella spp. in foods and faeces. However, a small but significant number of salmonella strains were missed by this method. The majority of these strains were detected when dulcitol was substituted by mannitol and tested on two separate Malthus conductance instruments. Some strains of Citrobacter freundii and Escherichia coli continued to give false positive results. Attempts are made to explain why the substitution of mannitol for dulcitol gives an improved medium.
Subject(s)
Culture Media , Feces/microbiology , Salmonella/isolation & purification , Electric Conductivity , False Positive Reactions , Galactitol/metabolism , Humans , Mannitol/metabolism , Salmonella/growth & developmentABSTRACT
The incidence of Vibrio parahaemolyticus in products of the Malaysian export shrimp processing industry was investigated through the stages from the catch to that of the cooked, peeled and frozen product. The organism was commonly found in freshly caught and landed shrimp, and could be detected by enrichment culture at all stages of processing. The number of V. parahaemolyticus in shrimp varied from nil to 4x10(4), and 19 of the 50 serotypes in the current antigenic scheme were found, O1-K38 and O1-K32 occurring most often. All the isolates were Kanagawa-negative; one strain was a sucrose-positive variant. The study indicated that specifications of 10(2) g-1 for V. parahaemolyticus in raw tropical shellfish are too stringent but that the Malaysian shrimp industry should be able to meet this requirement for cooked shrimp.
Subject(s)
Decapoda/microbiology , Food Microbiology , Vibrio parahaemolyticus/isolation & purification , Animals , Food Handling , MalaysiaABSTRACT
Recent work has showed high positive oxidation-reduction potential (Eh) values in fresh fish flesh, whereas strongly reducing conditions exist in fish viscera and spoiled fish flesh. The present study has demonstrated that this difference in measured Eh does not significantly influence growth and toxin production by Cl. botulinum type E. In comparison, storage temperature and the spore load in fish markedly influence toxin production. The public health significance of rapid toxin formation and high toxin titers demonstrated in ungutted fish is pointed out.
