CLARIFICATION OF THE STRUCTURE OF THE AMPICILLIN-RESISTANCE PLASMID RSF0885 FROM HAEMOPHILUS-INFLUENZAE HR-885 SEROTYPE-B

The nonconjugative ampicillin-resistance plasmid RSF0885 has been repo rted to be as small as 2.9 MDa and as large as 4.1 MDa with at least t wo restriction enzyme maps reported. In addition, the source of the or iginal plasmid has been reported to be Haemophilus influenzae and Haem ophilus parainfluenzae. Characterization of the source strains and seq uencing data of the plasmids revealed that H. influenzae serotype b wa s the original source strain and that IS1 -K in the larger plasmid was presumably acquired when the smaller plasmid was maintained in Escher ichia coli in S. Falkow's laboratory during the late 1970s.