Final full-text version of the paper available at: http://dx.doi.org/10.1128/AAC.50.4.1603-1607.2006.Two large conjugative resistance (R) plasmids from clinical strains of Salmonella enterica serovar Virchow carried a class 2 integron with the 5' conserved sequence (5'CS)-dfrA1-sat1-aadA1-3'CS gene array, which is associated with defective Tn7 transposons. In addition, each contained a different class 1 integron (with 5'CS-aadA1-3'CS or 5'CS-sat-smr-aadA1-3'CS gene arrays) linked to Tn21-Tn9 sequences, and several non-integron-associated R determinants. An intact copy of Tn7 (including the class 2 integron) was present in the chromosome of each strain.I. Rodríguez is the recipient of a grant from the Fundación para el Fomento en Asturias de la Investigación Científica Aplicada y la Tecnología (FICYT-BP04-086). The work was supported by projects FIS PI020172 (Ministerio de Sanidad y Consumo, Spain) and SAF2005-04212 (Ministerio de Educación y Ciencia, Spain).Peer reviewed