Correlation of the Polysaccharide Antigens of Francisella tularensis with Virulence in Experimental Mice

Abstract

Francisella tularensis gives rise to two distinct colony types, acriflavine agglutination test-positive (acr) and -negative (acr) colonies. The acf+ variants were exclusively low virulent in mice, while the acr variants were shown to be either high or low virulent. Three fractions, phosphate-buffered saline-extractable without heating, with heating at 60 C, and with heating at 100 C, were obtained from cultures of both the acr and acf- variants on agar media, and the polysaccharide antigens in those fractions were quantitated. All of the highly virulent acr variants possessed a large amount of the polysaccharide antigen in the fraction extractable with heating at 60 C. This antigen was not, however, detected in any of the acr variants and one low-virulent acr variant. It was also detected in a very low amount in some other acr variants with low virulence. The amount of this polysaccharide antigen was therefore shown to be correlated with bacterial virulence in mice. © 1995, Center For Academic Publications Japan. All rights reserved.