Molecular characterization and module composition of P22-related Salmonella phage genomes.

Genomes of newly isolated Salmonella phages were analysed by comparison of their EcoRI restriction patterns and by hybridization. Characteristic hybridization probes from reference phages P22, ES18 and E. coli phage lambda were chosen. Four probes selected from the lysis region examined the dispersal of the lambdoid lysis genes. Other probes characterized were the replication genes and part of the structural genes. The complex immunity region was investigated by means of hybridization as well as biological tests. The results showed the relationship of the isolated phages to the P22 branch of the lambdoid phages and revealed their modular genome organization consisting of different proportions of P22-related sequences. DNA restriction patterns of phages released from Salmonella strains sampled in limited geographical areas were significantly less heterogeneous than those of phages released from the worldwide sampled SARA collection. The use of prophage restriction patterns as a tool for the typing of Salmonellae to support the epidemiologic classification of pathogenic strains is discussed.