Phage-typing ofSalmonella weltevreden based on lysogeny I. The phage-typing system

All of the 1070 strains of Salmonella weltevreden tested were lysogenic, temperate phage being demonstrable in 83.9% of the strains in broth culture, 6.4% in mixed culture and the remaining 9.7% after induction by UV-irradiation and MC treatment. A phage-typing scheme for Salmonella weltevreden based on the host range of temperate phages was developed. The strains could be classified into eight groups by means of the host range of their temperate phages on six indicator strains and a ninth group, the symbiotic phages of which failed to lyse any of the indicator strains.