Large conjugative plasmids from clinical strains of Salmonella enterica serovar virchow contain a class 2 integron in addition to class 1 integrons and several non-integron-associated drug resistance determinants.

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.