Bacteriophage types of Salmonella typhi in the United States from 1974 through 1981.

From 1974 through 1981, 4,089 isolates of Salmonella typhi were phage typed at the Centers for Disease Control and nine regional laboratories in the United States. The most prevalent types were degraded Vi (27%), E1 (20.6%), A (9.8%), C1 (5.7%), untypable Vi (3.5%), W form (3.5%), D1 (3.4%), B3 (3.4%), and F1 (2.4%). There were less than 2% of each of the remaining types. The distribution of phage types for this time period was similar to that seen in the periods 1966-1969 and 1970-1973, except that phage type B3 was one of the 10 most prevalent types in 1974-1981 but was not seen in 1966-1973. Phage typing is presently the most valuable laboratory tool for differentiation of strains of S. typhi in epidemiological studies.