Further purification and characterization of high-molecular-weight polysaccharide from Pseudomonas aeruginosa

Previously published reports on high-molecular-weight polysaccharides from immunotype 1 and 2 of Pseudomonas aeruginosa indicated the presence of high levels of mannose in these preparations. This mannose has been found to be due to the presence of a yeastlike mannan in high-molecular-weight polysaccharide preparations. The source of the mannan was found to be the tryptic soy broth used to grow the bacteria. Mannan could be removed from the polysaccharide preparations by chromatography over columns of concanavalin A-Sepharose. The resulting polysaccharides had the same serological reactivity against rabbit antisera and the same immunogenic properties in mice as did the mannan-containing polysaccharides. Comparison of mannan-depleted polysaccharide with preparations of high-molecular-weight polysaccharide obtained from either ultrafiltered tryptic soy broth or a chemically defined medium showed that these polysaccharides were immunologically and chemically similar. Human immune responses to mannan-depleted polysaccharide from the immunotype 1 strain of P. aeruginosa were comparable with those previously seen in humans receiving mannan-containing polysaccharides. Thus, we found that P. aeruginosa high-molecular-weight polysaccharides prepared in either tryptic soy broth and then subjected to concanavalin A-Sepharose chromatography, ultrafiltered tryptic soy broth, or a chemically defined medium were immunologically and chemically comparable.