Molecular analysis of Greek and U.K. haemophilus influenzae plasmids

Ampicillin β-lactamase antibiotic resistance in Haemophilus influenzae is associated with the presence of large chromosomally integrated conjugative plasmids. The relationship between the plasmids of 10 beta-lactamase positive ampicillin resistant strains, 2 from the UK and 8 from Greece, was investigated. Extrachromosomal plasmids were detected and isolated after transfer to a rec-deficient recipient. Purified whole plasmid was used as probe. Also, a 12 kb Pst I fragment containing the putative point of re-circularisation in one plasmid, p1056, was cloned and used as probe. All plasmids also shared sequence homology with the 12 kb Pst I fragment containing the point of re-circularisation suggesting that sequences involved in excision and re-circularisation are conserved.