A Salmonella-specific DNA probe and its use in southern hybridization for differentiation of Salmonella enteritidis.

Chromosomal DNA from phage type 13a and Phage type 8 of Salmonella enteritidis (SE) was cloned in Escherichia coli using the plasmid pUC8. A 2.1-kilobase-pair (kbp) DNA fragment specific for Salmonella spp. was identified by colony, dot, and Southern hybridization analyses. When labeled and used as a probe (C7), this recombinant clone hybridized with the DNA of 18 Salmonella species but did not hybridize with the DNA of seven other enteric and non-enteric bacterial species. In Southern blot hybridization, this probe hybridized specifically to a 6.0 kbp BglI-digested DNA fragment of 17 SE isolates from human as well as avian sources, thus differentiating this fragment from DNA of 17 other Salmonella species. The C7 probe also hybridized to a 5-kbp fragment of one SE DNA derived from human and two SE DNA from poultry sources. This may indicate variation among SE isolates.