Classification of Vibrio vulnificus strains by the carbohydrate composition of their capsular polysaccharides

Pathogenic bacteria are often classified on the basis of the complex polysaccharides found on the surface, usually capsular polysaccharides or lipopolysaccharides. It is common in clinical practice to use reactivity with antisera specific to the various cell surface carbohydrates for this purpose. In this work, we describe a chemotyping method for bacterial capsular polysaccharides which is based on a carbohydrate analysis of an acid hydrolysate of the capsule. High-performance anion-exchange chromatography at high pH (HPAE) with electrochemical detection, which is used for analysis of the hydrolysate, shows preferential sensitivity for sugars. A single acid hydrolysis condition is chosen for screening a large collection of bacterial isolates and a computerized autosampler is used to make possible a large number of rapid analyses. This procedure does not yield a quantitative carbohydrate analysis for the sample but produces a fingerprint which can be used to discriminate among isolates which have different capsular polysaccharide structures. The procedure has been applied to a collection of 120 isolates of Vibrio vulnificus, a water-born species common in shellfish which causes septicemia in immunocompromised individuals, most often from eating of raw oysters. The collection of bacterial isolates includes strains from both clinical cases of septicemia and from such environmental sources such as sea water, sediments, and shellfish. Our results show that a number of unusual sugars including many amino sugars are found in these polysaccharides and that a wide variety of capsular carbotypes in V. vulnificus may be readily distinguished by the HPAE fingerprint.