O1 genotypes.

<p>The presence and absence of virulence-related genes are represented, respectively, by blue and white squares. The strains are grouped in colored bars according to their PFGE cluster (Fig. 4): from top to bottom are groups 1 (purple), 2 (red), 3 (blue), 9 (yellow), 6 (orange), and 8 (green). The colors highlighting the strain keys correspond to the isolation sources. Strains highlighted pink were isolated from wastewater, blue from superficial water, green from superficial stream water, and black from clinical sources.