Differentiation of Salmonella enteritidis and S. typhimurium by plasmid profile analysis and restriction endonuclease analysis of chromosomal DNA.

Infections with Salmonella enteritidis and S. typhimurium are frequent causes of food-borne diseases in man and are responsible for considerable economic losses in the poultry industry (Fantasia et al., 1991; Pohl et al., 1991). Methods for the more careful differentiation and typing of these two serotypes are necessary for the investigation of the spread and transmission of the infection. Conventional methods of Salmonella differentiation (bioassays, phage-typing, resistance to antibiotics) often lack the necessary resolution potential (Wray et al., 1987). Plasmid profile analysis and restriction analysis of chromosomal DNA, based on restriction fragment length polymorphism (RFLP) have been used for the differentiation of Salmonellae (Wray et al., 1987; Nastasi et al., 1988; Franklin et al., 1990; Helmuth von et al., 1990; Martinetti and Altwegg, 1990). Rapid and unsophisticated analysis of the content of plasmid DNA tends to be preferred. However, some strains lack plasmids or may lose them during laboratory passages (Nastasi et al., 1988; Hartstein et al., 1991). On the other hand, restriction analysis of chromosomal DNA yields more constant and reliable information on bacterial strains (Tveten et al., 1991). The aim of this study was to compare 18 field strains of S. enteritis and 12 strains of S. typhimurium on the basis of plasmid profile analysis and restriction endonuclease analysis of chromosomal DNA. Plasmid DNA content was determined and chromosomal DNA, isolated from bacterial cells immobilized in low-melting agarose, was digested with restriction endonuclease Pst I in 18 and 12 field strains of S. enteritidis and S. typhimurium, respectively. The resulting fragments were separated by pulse-field electrophoresis in agarose gel.(ABSTRACT TRUNCATED AT 250 WORDS)