Restriction and hybridization analysis of serotype Typhimurium virulence plasmids. (A) Plasmid restriction profiles generated by HindIII, ClaI, and EcoRI (fragment sizes in kilobases). (B) Successive hybridizations of digested DNA with virulence plasmid gene probes (a, traT; b, rck; c, spvC) and resistance gene probes [d, merA; e, int1; f, oxa1; g, aadA1; h, qacΕΔ1-sul1; i, catA1; j, tet(B)]. Lanes: λ, phage lambda DNA digested with PstI (fragment sizes in kilobases); 1, pSLT90 from LT2; 2, pUO-StVR2 from E. coli CT31 transconjugant. Chr, chromosomal DNA.