Figure 1

Schematic diagram showing some of the strategies for screening for various genetic elements and for interrogation between these elements and resistance genes. The targets of each primer and the direction of PCR amplification is shown using arrows. PCRs were done both in the 5’ and in the 3’ orientation for each pair of genes tested. A: The strategy used for detection and characterization of class 1 integrons. B: The strategy used for detection and characterization of class 2 integrons and their physical linkage to Tn7. C: An example of the strategy used for analysis of physical linkages between class 1 integrons and Tn21 and to IS26. The primer positions for screening of Tn21 transposition genes. D and E: An example of the strategy used for analysis for physical linkages between integrons, ISCR1 and bla genes. F: An example of the strategy used for analysis for physical linkages between integrons, ISEcp1, IS26 and bla genes. These illustrations are based on PCR mapping data and not sequencing. Therefore, the sizes of each gene and the distances between any two genes are not drawn to scale.