Lack of Deoxyribonucleic Acid Relatedness Between Haemophilus ducreyi and Other Haemophilus Species

Deoxyribonucleic acid relatedness studies (S1 nuclease method) showed that 25 strains of Haemophilus ducreyi from diverse geographic origins form a homogeneous deoxyribonucleic acid hybridization group. A total of 17 type or reference strains of established or proposed Haemophilus species were 0 to 6% related to H. ducreyi at the optimal temperature. These findings do not support the assignment of H. ducreyi to the genus Haemophilus.