Epidemiological analysis of Salmonella typhi-murium infections on the basis of laboratory methods. I. Distribution of phage types and biotypes of Salmonella typhi-murium isolated in Hungary in the period 1960 to 1981.

Phage and biochemical types were determined of 34 937 Salmonella typhi-murium cultures including 31 708 human strains, 2732 animal strains and 497 strains isolated from water. Phage type 4, not typable strains (nt) and phage type 2b were predominant among the strains of human and animal origin, and nt, 4 and 2b among the strains isolated from water. The most frequent phage types and the nt strains were subdivided by biotyping and additional phages. The incidence of S. typhi-murium var. copenhagen strains was 12.4%, they belonged mainly to phage types 2b and nt. The number of S. typhi-murium isolates of human origin showed a 2-4 year periodical fluctuation between 1960 and 1981. A connection was found between the incidence of the predominant phage types (4, nt, 2b) and the periodical changes in the total number of isolates. Phage type 4, which predominated among the strains of human and animal origin till 1976, was ousted gradually by nt ones. In the period when the change in predominance was observed the number of epidemics decreased and the number of sporadic cases increased. The change in the frequency of phage types took place at the same time when the frequency of phage types changed among the strains isolated from cattle and meat-products (4----nt). The increased number of sporadic cases after 1976 refers to infections from cattle and not from poultry.