TABLE 1.

Ceftriaxone-resistant Salmonella strains used in the study

StrainSerotype (PFGE type)Antibiotic resistance phenotypeaE. coli backgroundbAntibiotic resistance phenotype of E. colicPlasmid typeState of originYr of isolation
1041Newport (A)ACSSuTCroFxD10Same as wild typeCNebr.1999
5313Newport (A)ACSSuTCroFxCMinn.1999
5501Newport (A)ACSSuTCroFxDHSame as wild typeCN.J.1999
5653Newport (A)ACSSuTCroFxCFla.1999
7073Newport (A)ACSSuTCroFxD10Same as wild typeCMass.1999
7075Newport (A)ACSSuTCroFxCMass.1999
7079Newport (A)ACSSuTCroFxCMass.1999
7467Newport (A)ACSSuTCroFxCOreg.1999
8611Newport (A)ACSSuTCroFxD10Same as wild typeCTenn.2000
8683Newport (A)ACSSuTCroFxD10Same as wild typeCWash.2000
6163Newport (B)ACSSuSxtTCroFxCGa.1999
7040Newport (B)ACSSuSxtTCroFxD10All except SxtCMass.1999
7041Newport (B)ACSSuSxtTCroFxCMass.1999
5561Newport (C)ACSSuTCroFxC6Same as wild typeCN.Y.1999
6100Newport (C)ACSSuTCroFxCCalif.1999
712Newport (D)ACSSuSxtTCroFxD10All except SxtCNebr.1999
2231Newport (D)ACSSuSxtTCroFxD10Same as wild typeCNebr.2000
4962Newport (E)ACSSuTCroFxD10Same as wild typeCColo.1999
5299Newport (E)ACSSuTCroFxCColo.1999
5924Newport (F)ACSSuTKCroFxD10Same as wild typeCKans.1999
6980Newport (G)ACSSuTCroFxDHSame as wild typeCN.J.1999
10091Newport (H)ACSSuTCroFxD10Same as wild typeCMd.2001
2050Newport (I)ACSSuTCroFxD10Same as wild typeCNebr.2000
5436TyphimuriumACroFxD10BSame as wild typeBGa.1999
5655TyphimuriumACSSuTCroFxD10Same as wild typeCFla.1999
5678TyphimuriumACSSuTCroFxC6Same as wild typeAKans.1999
5927TyphimuriumACSSuTCroFxC6All except SSuTBKans.1999
5965TyphimuriumACroFxC6Same as wild typeBConn.1999
6191TyphimuriumACroFxC6Same as wild typeBGa.1999
6516TyphimuriumACroFxC6Same as wild typeBN.J.1999
1568TyphimuriumACSSuTCroFxD10Same as wild typeANebr.2000
2000TyphimuriumACSSuTKCroFxD10Same as wild typeANebr.2000
2232TyphimuriumACSSuTCroFxD10Same as wild typeANebr.2000
2042AgonaACSSuSxtTCroFxD10Same as wild typeANebr.2000
2151ReadingACSSuTKCroFxD10All except KANebr.2000
  • a Abbreviations: A, ampicillin; C, chloramphenicol; S, streptomycin; Su, sulfisoxazole; Sxt, trimethoprim-sulfamethoxazole; T, tetracycline; K, kanamycin; Cro, ceftriaxone; Fx, cefoxitin.

  • b Background to which plasmid was transferred via conjugation (C6), transformation (DH), or electroporation (D10).

  • c “All except” indicates resistance to the same antimicrobial agents as the wild-type Salmonella strain, except for the particular antimicrobials noted. “Same as wild type” indicates resistance to the same antimicrobial agents as the wild-type Salmonella strain.