Detection of Gene Cassettes in Tn 402 -Like Class 1 Integrons

Detection of Gene Cassettes in Tn402-Like Class 1 Integrons ᰔAmplification of the gene cassettes in class 1 integrons by PCR using primers in the 5Ј conserved segment (5Ј-CS) and the 3Ј-CS (7, 8) has been used in hundreds of studies to identify integron-associated resistance genes (Fig. 1A).Equivalent PCR primers that detect cassettes in class 2 integrons, i.e., Tn7 family transposons (18), are also widely used.The approach used to detect integrons in antibiotic-resistant bacteria is to screen for the intI genes, using primers internal to these genes, and then amplify the cassettes in intI-positive strains by use of primers in the flanking conserved regions.Because different cassettes can have the same size and the arrays can include more than one gene ( 16), amplicon size alone cannot identify