Occurrence of Two Immunological Groups Within the Genus Listeria. Studies Based upon Precipitation Reactions

Abstract

The precipitation reactions of 16 strains of L. monocytogenes were studied. Polysaccharides were extracted from the bacterial cell according to the method of Fuller and precipitated against antibacterial sera prepd. in rabbits. When antiserum was overlayed with an equal volume of the specific soluble substance, a compact, disc precipitate formed within 10-15 min. at room temp. Precipitin tests were carried out also using various dilutions of the specific soluble substance, incubated in a water bath at 37[degree] C for 2 hrs., and then placed in the refrigerator overnight after which time the tubes were examined for the presence or absence of precipitate. On the basis of the immunological reactions the 16 strains of L. monocytogenes were divided into 2 groups, namely a rodent and a ruminant group, which is consistent with the classification as suggested by agglutinin and agglutinin absorption studies. Strains isolated from meningitis and encephalitis occurring in man were identified with one or the other of these groups. The precipitin test affords a simplified technique for the identification and immunological classification of the members of the genus Listeria.