Distribution of phagovars of Salmonella typhimurium in Canada (1969-1976)

The distribution of Salmonella typhimurium phagovars in Canada during the period 1969-1976 is described. Of 9282 strains examined, 69.6% were of human origin and the remaining 30.4% were isolated from non-human sources. The typable strains of all sources, constituted 73.1% of all strains examined, and were representative of 107 different phagovars. There were only 15 phagovars accounting for more than 1% of the cases either from human or non-human sources. Phagovar 49 consistently showed the highest incidence in both groups (human 25.2% and non-human 19.9%). Although 26.6% of the strains from all sources were not typable, the use of experimental phages M 499 and 721 reduced the percentage of untypable strains to 9.9%. Yearly data on the incidence of phagovars from human sources showed a gradual decrease of phagovar 49 and an increase of phagovar 10. Examination of 358 human outbreaks of S. typhimurium revealed 47 different phagovars during the 8-year period.