Relation of capsular materials and colony opacity to virulence of Vibrio vulnificus

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Abstract
Colonies which varied in opacity were isolated from the 4 strains of V. vulnificus. Opaque and translucent colonial types of the strains were distinguished from the corresponding parent strains. Variation in the opacity of colonies formed by each strain was accompanied by variation of capsular material formation, which was clarified by EM of the organisms stained with ruthenium red. The opaque-type colonies of the strains had capsular materials. Three translucent-type colonies had no observable capsular materials, and 1 had incomplete capsular materials, in contrast to the corresponding opaque type. The corresponding opaque and translucent types of the strains were compared for points of virulence in mice and guinea pigs. By having capsular materials, the bacterial strains acquired resistance to serum bactericidal action, antiphagocytic activity, high lethality for mice and strong invasiveness in the s.c. tissue of guinea pigs. Capsular materials of V. vulnificus were considered to be important for the expression of virulence.