A NEW DANISH LISTERIA-MONOCYTOGENES PHAGE TYPING SYSTEM

A phage typing system was developed for Listeria monocytogenes. Phages were released from clinical and from food strains of L. monocytogenes by mitomycin C induction. The system consists of two subsystems, one of which is used to type L. monocytogenes serotype 1 strains, containi ng 12 phages, and a second which is used to type serotype 4 strains, c ontaining 14 other phages. For the serotype 1 subsystem, the reproduci bility was greater-than-or-equal-to 90%, the typability 92%, and the d iscriminatory power, as judged by the discriminatory index, 80%. The c orresponding figures for the serotype 4 subsystem were: reproducibilit y greater-than-or-equal-to 94%, typability 87%, and discriminatory ind ex 87%. The performance of the whole typing system is sufficient for i t to be used for screening purposes.