Figure 2

Distribution of plasmids in 254 S. aureus (198 human isolates and 55 animal isolates) using microarray. Presence or absence of each gene (listed on left) in each isolate is depicted by colour. The colour is an indicator of test signal over reference signal ratio. Thus, (i) yellow indicates presence of the gene in both test strain and reference strain, (ii) red indicates presence of the gene in the test strain but not in the reference strain, (iii) blue indicates absence in the test strain but not the reference strain, and (iv) grey indicates absence in both the test and reference strains. Genes with white signals are very low intensity and regarded as negative for both strains. The colour intensity is an indicator of signal intensity, and this can differ because (i) the homology of the probe, which can be hundreds of base pairs long, and DNA may vary, and (ii) copy numbers may vary. Isolates (represented vertically) are clustered into lineages [14]. For each isolate, its mammalian host of origin and its lineage (clonal complex) are shown at the bottom of the figure. Human isolates are coloured light blue (invasive) and dark blue (carriage). Animal isolates are coloured red (cow), pink (horse), maroon (sheep and goat) and white (camel). The figure shows that rep genes and resistance genes are distributed in a lineage dependent manner.