[Epidemiology and phage typing of Salmonella typhimurium in Austria 1980-1982]

From 1980 to 1982 a total of 4541 strains of S. typhimurium of human origin and 745 S. typhimurium of non-human sources were received by the Salmonella Centre. During this period, the percentage of S. typhimurium rose from 33% to 51% (human origin) and from 12% to 33% (non-human origin), respectively. The incidence of infection was 20.0, the regional distribution showed a prominence of the eastern and western parts of Austria with Styria as leading country (46.2). 60% of the isolates of S. typhimurium were associated with illness, which was 10% more than for the other salmonellae; concerning outbreaks as well as single cases, S. typhimurium dominated, whereas the proportion of carriers of S. typhimurium among foodhandlers was small (12% S. typhimurium, 31% other salmonellae). As to the age-specific attack-rate, children younger than 5 years by far predominated with 67.2, with a falling tendency in the other age groups. As far as food is concerned, the increase of S. typhimurium in poultry is particularly striking. According to the phage-typing results, LT 10 was prominent in the years 1980 and 1981, whereas in 1982, LT 66, accounting for 62% out of 2201 tested human isolates dominated among 44 different phage-types as epidemic strain, especially in Styria and eastern Austria. In addition, LT 10 and LT 3 could be found more frequently. Starting from the important role of food in Salmonella associated enteritis, LT 66 leads to chicken as the main source of infection. Apart from LT 66, LT 1, 2, 3 and LT 140 were more frequent in non-human isolates. This infiltration of LT 66 into the Austrian chicken industry could have its origin in imported parent chickens. As mechanism the single replacement of LT 10 by LT 66 is discussed as well as the phage-conversion of LT 10. The other possible chains of infection (other poultry, feeding-staff, man) are regarded as less probable. To prove this thesis investigations on plasmids should be done.