Molecular Epidemiology ofBeta-Lactamase-Specifying Plasmids ofHaemophilus ducreyi

Wehavestudied thegenetic basis ofbeta-lactamase production ineight strains ofHaemophilus ducreyi isolated indiverse areas oftheworld. Beta-lactamase production inallstrains wasmediated byplasmids having amolecular massof either 5.7or7.0megadaltons. Plasmids of5.7megadaltons wereshowntocarry theentire sequence ofpFA7,thebeta-lactamase specifying plasmid foundin isolates ofNeisseria gonorrhoeae epidemiologically linked toWestAfrica. Plasmids of7.0megadaltons wereshowntocarry theentire sequence ofpFA3, thebeta-lactamase specifying plasmid foundinFarEastern isolates ofN. gonorrhoeae. Bothgroups ofH.ducreyi plasmids wereshowntocarry physically complete andfunctional TnAsequences. Thuswehaveidentified twotypes ofH. ducreyi beta-lactamase plasmid whichareidentical tothetwotypesofN. gonorrhoeae beta-lactamase plasmid, except thattheycarrycomplete TnA sequences. Wehavepreviously characterized theplasmid pJB1, which wasfound tomediate TEM-1betalactamase production inastrain ofHaemophilus ducreyi isolated inWinnipeg, Canada(7,20). This plasmid carries 75%ofthesequences presentonpMRO360, the4.7-megadalton (Mdal) plasmid which mediates beta-lactamase production inisolates ofNeisseria gonorrhoeae epidemiologically linked totheFarEast(6,7,24,26, 30). Inaddition, pJB1wasfoundtocarry a complete andfunctional TnAsequence which appeared identical toTn2onthebasis ofrestriction enzymeanalysis (6). Studies ofthegenetic basis ofbeta-lactamase production inN.gonorrhoeae strains isolated fromdiverse geographic areas haveshownthat itismediated either by 4.7-Mdal plasmid species identical topFA3 (pMRO360) orbya3.4-Mdal species identical to pFA7(pMRO200), theplasmid found inisolates originally epidemiologically