PCR amplicons of STEC integrons. Lanes 2 to 5 were generated with the CS primers specific for class 1 integron. Lanes 6 to 9 were obtained using the sul primers specific for the sul gene that confers sulfonamide resistance. Lanes 10 to 13 were obtained using the primers specific for integrase. Specifically, lanes 2, 6, and 10 show positive controls (serovar Typhimurium DT104); lanes 3, 7, and 11 show E. coli O111:H8 strain CVM1877; lanes 4, 8, and 12 show E. coli O157:H7 strain CVM990; and lanes 5, 9, and 13 show negative controls (E. coli K-12).