Multiple typing of Salmonella typhimurium isolates: an epidemiological study.

An epidemiological study was carried out on sixty-four Salmonella typhimurium strains isolated in Palermo during the period January-July 1987 and identified at the Southern Italy Center of Enterobacteriaceae. These included 5 isolates from a small food-poisoning outbreak, which resulted antibiotic susceptible, not colicinogenic and untypable by the phage-type scheme of Anderson. Plasmid profile analysis was not a reliable method to differentiate them from non epidemic strains. The 5 epidemic isolates, belonging to biotype 25a, were assigned into NT 2 phage-type by an accessory set of phages developed in this laboratory. Such biotype/phage-type association was never detected in the remaining Salmonella typhimurium strains isolated during the first 7 months of 1987. Chromosomal DNA analysis provided additional information on the relationships among Salmonella typhimurium isolates.