FIG. 1.

(a) Genetic map of a class 1 integron (adapted from reference 25). The filled areas are the conserved regions at the 5′ and 3′ ends of the integron. The open arrows between the conserved regions represent the inserted gene cassettes (two are illustrated here). The intI1 gene and the bulk of the att1 site used for recombination are located within the 5′ conserved region. The genes qacEΔ1 (a defective quaternary ammonium cation that encodes resistance to disinfectants), sul1 (which encodes sulfonamide resistance), and ORF5 (open reading frame 5) are encoded within the 3′ conserved sequence. (b) Schematic map indicating primer annealing sites for the primers used in the screening reaction (primers L2 and L3) and confirmatory reactions (primers L1, L2, and R1). Primers L1 and R1 anneal at positions 1190 to 1206 and 1342 to 1326, respectively, in the published sequence of integron In0 (GenBank accession number M73819) (4). In the same sequence, L2 anneals at positions 910 to 926 and L3 anneals at positions 1206 to 1190.