The pathogenicity of haemophilus ducreyi, the etiological agent of chancroid is poorly understood. Although h.ductreyi appears not to invade the bloodstream, resistance to lysis by normal human serum may allow prolonged multiplication of the organism within tissues. The determinants of serum resistance, however, remain to be elucidated and could include a number of bacterial surface components including outer membrane proteins (OMPs) and lipopolysaccharide
