Serotyping of strains belonging to the Citrobacter-Levinea group isolated from diagnostic material

A proposal is presented for the serotyping of Citrobacter-Levinea strains: 9 serotypes for Citrobacter diversus (Levinea malonatica) and 13 serotypes for H2S-negative, indole-positive variants of Citrobacter freundii (Levinea amalonatica), which showed a considerable antigenic diversity. By means of both kinds of antiserum types 80 per cent of the strains (L. malonatica 100 per cent, L. amalonatica 72 per cent) from a series of 106 strains isolated from different diagnostic material were serologically classified. According to results presented in this paper, a direct relationship between biotype and serotype was found among the strains of biotype b for Levinea amalonatica and c for L. malonatica, which were agglutinated by the antisera prepared from biotypes b and c, respectively, only. Serotyping will evidently greatly contribute to a more perfect identification, especially of those strains that are, for various reasons, classified among so called intermediates. The importance of the Citrobacter freundii and C. diversus species in the clinical material is emphasized with a view to their increasing occurrence. Taxonomic and nomenclature questions with regard to Citrobacter-Levinea are discussed in detail.