Molecular characterization of resistance plasmids in epidemiologically unrelated strains of multiresistant Haemophilus influenzae

J Infect Dis. 1993 Jul;168(1):177-87. doi: 10.1093/infdis/168.1.177.


Thirty-three epidemiologically unrelated strains of ampicillin-chloramphenicol-resistant isolates of Haemophilus influenzae (22 type b, 11 unencapsulated), isolated over 10 years in Belgium, were compared with 53 ampicillin-resistant chloramphenicol-susceptible isolates (22 type b, 31 unencapsulated). All ampicillin-chloramphenicol-resistant and 76% of ampicillin-resistant chloramphenicol-susceptible strains were resistant to tetracycline, kanamycin, or both. Resistance to these antibiotics was specified by a 37- to 44-MDa conjugative plasmid. The genetic relatedness of these plasmids and of those in multiresistance strains from Spain was investigated. Plasmids specifying ampicillin-chloramphenicol-tetracycline-kanamycin resistance in Belgium or in Spain had highly related restriction fragment patterns. By homoduplex analysis, they had similar molecular organization and contained a structure identical to Tn10-TnCm, a transposon previously identified in chloramphenicol-tetracycline-resistant H. influenzae. Plasmids coding for different resistance phenotypes had less resemblance by restriction endonuclease analysis; however, study of heteroduplex molecules indicated they shared a high proportion of core sequences. These findings support the hypothesis of independent transposition events resulting in resistance plasmids of close molecular organization.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Belgium / epidemiology
  • Conjugation, Genetic
  • Drug Resistance, Microbial / genetics
  • Haemophilus Infections / epidemiology
  • Haemophilus Infections / microbiology
  • Haemophilus influenzae / classification
  • Haemophilus influenzae / drug effects
  • Haemophilus influenzae / genetics*
  • Haemophilus influenzae / ultrastructure
  • Microscopy, Electron
  • Phenotype
  • Polymorphism, Restriction Fragment Length
  • R Factors* / ultrastructure
  • Spain / epidemiology