Analysis of the Salmonella typhimurium isolates from food-poisoning cases by molecular subtyping methods Original Research Article

Salmonella typhimurium is one of the common food pathogens which may cause gastroenteritidis in human. In order to find the prevalent and recirculating strains of S. typhimurium which caused food-poisoning diarrhoea cases in northern Taiwan, 45 randomly selected S. typhimurium strains isolated from food-poisoning cases during 1991–1994 were subjected to pulsed field gel electrophoresis (PFGE), plasmid profile and random amplified polymorphic DNA (RAPD) analysis. Results showed that when genomic DNAs of these Salmonella strains were digested with XbaI, AvrII and SpeI, respectively, followed by PFGE, a total of 26 PFGE patterns combinations were observed. Of them patterns X5A4S4 and X2A2S2 were the major patterns since they contained 13 and four strains, respectively. For plasmid profiles, 21 patterns were found. When plasmid profiles were combined with PFGE patterns, a total of 35 subtypes were found and strains of the subtype of X5A4S4e7 (seven strains) and X2A2S2e7 (three strains) were the prevalent strains. Subtyping by RAPD could not further differentiate these strains grouped by PFGE and plasmid profiles. Since strains of the same patterns combinations were isolated from unrelated food-poisoning cases during 1991–1994 in northern Taiwan, these strains may be the prevalent strains and recirculation of these strains for food-poisoning cases is possible.