Selective inhibition of certain enteric bacteria by selenite media incubated at 35 and 43 C

Selenite broth (SB) is a useful enrichment medium for isolating certain salmonellae and arizonae from specimen materials contaminated with competitive bacteria. Pure cultures of pseudomonas, proteus, and some coliform strains were suppressed more markedly by SB media containing additional selenite than the salmonellae and arizonae tested. Some very closely related organisms showed conspicuously different results and whereas many serotypes of Escherichia coli were inhibited, others flourished in the test environments. Selenite media were more toxic to some salmonellae than to others, and Salmonella choleraesuis, S. gallinarum, S. pullorum, and S. typhi did not grow well, especially at 43 C. Selenite broth incubated at 43 C proved to be more toxic to all test cultures than incubation at 35 C, but in general the salmonellae and arizonae were inhibited less than the extraneous bacteria with which they are often associated.