Molecular epidemiology of beta-lactamase-specifying plasmids of Haemophilus ducreyi.

We have studied the genetic basis of beta-lactamase production in eight strains of Haemophilus ducreyi isolated in diverse areas of the world. Beta-lactamase production in all strains was mediated by plasmids having a molecular mass of either 5.7 or 7.0 megadaltons. Plasmids of 5.7 megadaltons were shown to carry the entire sequence of pFA7, the beta-lactamase specifying plasmid found in isolates of Neisseria gonorrhoeae epidemiologically linked to West Africa. Plasmids of 7.0 megadaltons were shown to carry the entire sequence of pFA3, the beta-lactamase specifying plasmid found in Far Eastern isolates of N. gonorrhoeae. Both groups of H. ducreyi plasmids were shown to carry physically complete and functional TnA sequences. Thus we have identified two types of H. ducreyi beta-lactamase plasmid which are identical to the two types of N. gonorrhoeae beta-lactamase plasmid, except that they carry complete TnA sequences.