A Multi-resistance Plasmid Isolated from Commensal Neisseria Species is Closely Related to the Enterobacterial Plasmid RSF1010

pFM739, an R plasmid from Neisseria sicca that encodes penicillin, streptomycin and sulphonamide resistance, and the enterobacterial IncQ(P-4) plasmid RSF1010, which encodes streptomycin and sulphonamide resistance, were incompatible, and were mobilized by the same conjugative plasmids. Restriction mapping confirmed a high degree of similarity between both R plasmids; pFM739 carried DNA fragments corresponding to the known replication and resistance regions of RSF1010. pFM739 also carried an extra segment with the same restriction map as that described for the beta-lactamase-coding region of transposon Tn3. It is suggested that the R plasmids isolated from commensal Neisseria sp. could have resulted from transposition of a Tn3-like genetic element to an RSF1010-like plasmid, and that they contain deletion derivatives of transposon Tn3.