Serologic Typing of Listeria monocytogenes by Gel Diffusion Using Thermostable Antigens

Abstract

Using acid extracts of capsular enhanced organisms typing of the genus was possible. Types n, Va and IVb gave a monospecific response. Types I and III gave a specific pattern for identification. Sixty strains tested were placed in 5 serotypes that coincided with the results obtained with the conventional somatic "O" and flagellar "H" antigens. As evidenced by gel diffusion L. monocytogenes contains a complex system of thermostable antigens. The preparation of immune sera and problems in obtaining a monospecific response are discussed. The lack of cross reactions experienced with the conventional agglutination technic is outlined. The technic does not require absorption of the immune sera. It is possible that the method can be used by large facilities other than specific typing centers.