CHARACTERIZATION OF A PLASMID CODIFYING THE SYNTHESIS OF A BETA-LACTAMASE PRODUCED BY SHIGELLA-FLEXNERI

The resistance to beta-lactam antibiotics shown by a strain of Shigell a flexneri was plasmid-coded. This plasmid, pMAM-1, when transferred t o Escherichia coli K-12 by conjugation, presented the same molecular w eight (100 kbp) and conferred the same high level of resistance to amp icillin in the transconjugant as in the wild type strains (MIC, 2048-4 096). Restriction analysis of the plasmid in transconjugants revealed various restrictive sites to some endonucleases (i.e. Bam HI, Eco RI, Pst I, Nco I, Cla I, Sf I and Sau 3AI, Nhe and Hin dllI), and no restr ictive sites at ail for other endonucleases (such as Xho I, Dra I, Kpn I, and Sal I), Some restricted DNA fragments were appropriate for clo ning and isolation of the beta-lactamase gene present in Shigella flex neri UCSF 129. This work provides the first step in this direction.