Differences in blood group B-specific mucinase activity between virulent and avirulent Shigella flexneri 2a strains

Abstract

Based on our previous findings we postulate that the production of blood group B-degrading mucinase by Shigella flexneri 2a is related to virulence. The virulent S. flexneri 2a strain M4243 produced a blood group B mucinase which decreased the blood group B reactivity of germfree mouse mucins by a factor of 16 and the B reactivity of human saliva by a factor of 32. Avirulent S. flexneri 2a B-1, serologically similar, but not genetically identical to the M4243 strain, failed to degrade the blood group reactivity. The mucin-degrading ability of S. flexneri 2a M4243 harboring a large virulence-conferring 140 MDa plasmid was then compared with a genetically similar large plasmid-free avirulent S. flexneri 2a M4243A 1. Virulent S. flexneri M4243 grew in human salivary mucins while the genetically identical avirulent M4243A 1 did not. Supernatant of virulent M4243 culture decreased the blood B reactivity of salivary mucins by a factor of 32 while the avirulent M4243a 1 had no effect. Eleven of 12 colonies of the transconjugant hybrid Escherichia coli K12 (7300-1-5) containing the shigella PWR 110 plasmid and chromosomal markers decreased the blood group B reactivity by a factor of 4-32, and two of four colonies of the E. coli strain 7262 containing only the plasmid reduced the B reactivity by a factor of 4–16. These findings suggest that blood group B-specific mucinase production may be related to S. flexneri virulence.