Restriction enzyme map of cryptic plasmid accompanying pR711b and pR409; identity of pR409 and pR388

Abstract
A reference strain containing the IncW plasmid, pR409, was found to contain also a cryptic, conjugative plasmid, here named pJR15. After the separation of the two plasmids into different strains of bacteria, pR409 was found to have an identical restriction enzyme map to the IncW plasmid, pR388. Both pR409 and pR388 were isolated from the same hospital in London and confer sulphonamide and trimethoprim resistance. Orginally pR409 was reported to confer resistance to tetracycline, but this was not confirmed by the Plasmid Reference Center. pR409 appears to represent another isolate of pR388 in a different host background. The restriction enzyme map of the cryptic plasmid, pJR15 (39 kb), has been determined. pJR15 was found compatible with plasmids from 15 different incompatibility groups and has been found also in the reference strain of the IncD plasmid, pR711b. The HindIII and BglII digests of pR711 b are shown. The possible presence of the conjugative plasmid, pJR15, should be examined for studies on the sex pili or chromosomal mobilization properties of pR711b.