ABSTRACT
The region of DNA encoding the mannose-fucose-resistant hemagglutinin (MFRHA) of Vibrio cholerae O1 has been localized, and the nucleotide sequence has been determined. The region contains a single open reading frame encoding 230 amino acids, corresponding to a protein of 26.9 kDa. The N terminus of this protein is atypical for a protein localized in the outer membrane. A mutant lacking MFRHA activity has been constructed by allelic exchange after inactivation via the insertion of a kanamycin resistance gene cartridge. The MFRHA-negative mutant has been assessed for virulence in the infant mouse cholera model. This mutant shows a marked defect in its ability to persist in the infant mouse gut and is incapable of competing with the wild-type organism, even when given in 25-fold excess. This defect also leads to a > 100-fold increase in the 50% lethal dose. These data suggest that the MFRHA is an important colonization factor in the infant mouse model.
