A Comparative study on Two Enrichment Media for the Isolation of Salmonella spp. from Foods for Export

Two enrichment media, tetrathionate broth (TT broth) and selenite cystine brpth (Se broth), for isolating salmonellae from frozen seafood products, have been evaluated on the basis of selectively promoting growth of salmonellae at the incubation temperature of 37 degree C. A total of 6,772 food samples were investigated with the positive results of 56 samples from TT broth, 20 samples from Se broth and 26 samples from both media. Percentage of Salmonellae detection from TT Broth and Se broth were 80% and 46% of the positive samples respectively. It was not the intention of the investigators to imply that only TT broth is adequate for the isolation of all salmonellae from deferent types of food, it is incontrovertibly shown that both enrichment broths are necessary to obtain a maximum number of positive isolations because TT broth gave negative result of 20% of the positive samples. The factors possibly affected the detection of salmonellae using TT broth and Se broth other than the quality of media themselves are as follows: the species of Salmonella contaminated in food samples, the number of coliforms present in food samples, types of physical treatments in processing that cause damage to salmonella cells and pH of food samples investigated. Key words: Secondary enrichment media, Salmonella.