Abstract
Twenty-one strains of Haemophilus ducreyi were analysed by Western blotting using two antisera produced in mice. Common antigens of molecular weights 58, 46, 41, 28, 22 and 16 kDa were detected in all the strains. The antigens were protein in nature, since they could not be detected in whole-cell lysates which had been treated with proteinase K. The H. ducreyi strains showed antigenic cross-reactivity with strains of H. influenzae and H. parainfluenzae, but showed minimal or no cross-reactivity with seven other species of bacteria.