FIG. 2.

Fluoroquinolone resistance occurs in genetically diverse avian E. coli isolates. Similarities among E. coli RAPD patterns were identified by cluster analysis using the neighbor-joining method to draw a phylogenetic tree (13). E. coli isolates with similar RAPD patterns were placed into the same cluster or branch and designated as an RT. Phylogenetic analysis identified 16 RTs based on differences in RAPD patterns among 184 avian E. coli isolates that have been previously described (13). An asterisk indicates an RAPD type identified among fluoroquinolone-resistant avian E. coli isolates.