PFGE dendrogram showing clustering (by UPGMA and the Dice coefficient) of all GREF and GSEF PFGE types recovered from two poultry farmers and their poultry on three different occasions(fall 1998, spring 1999, and fall 1999). The strains were grouped into 52 different PFGE types (including 11 PFGE subtypes, indicated with a letter following the type number). A total of 24 PFGE types were isolated on more than one occasion and/or recovered from both poultry and farmer fecal samples. The strains were named according to the farm from which they were isolated (399 or 64), the time of isolation (F98, S99, or F99), and whether they were of animal (A) or human (H) origin. Glycopeptide-susceptible strains were labeled with an āSā (susceptible). The bandwidth tolerance was critically set at 1.5%.