Salmonella enterica serovar Enteritidis-lysing bacteriophages isolated from poultry or human sewage sources were used to reduce Salmonella Enteritidis in vitro and in experimentally infected chicks. Cocktails of 4 different bacteriophages obtained from commercial broiler houses (CB4Ø) and 45 bacteriophages from a municipal wastewater treatment plant (WT45Ø) were evaluated. In experiment 1, an in vitro crop assay was conducted with selected bacteriophage concentrations (10(5) to 10(9) pfu/mL) to determine ability to reduce Salmonella Enteritidis in the simulated crop environment. Following 2 h at 37 degrees C, CB4Ø or WT45Ø reduced Salmonella Enteritidis recovery by 1.5 or 5 log, respectively, as compared with control. However, CB4Ø did not affect total SE recovery after 6 h, whereas WT45Ø resulted in up to a 6-log reduction of Salmonella Enteritidis. In experiment 2, day-of-hatch chicks were challenged orally with 3 x 10(3) cfu/chick Salmonella Enteritidis and treated cloacally with 1 x 10(9) WT45Ø pfu/chick 1 h postchallenge. One hour later, chicks were treated or not with a commercially available probiotic (Floramax-B11). Both treatments significantly reduced Salmonella Enteritidis recovery from cecal tonsils at 24 h following vent lip application as compared with controls, but no additive effect was observed with the combination of bacteriophages and probiotic. In experiment 3, day-of-hatch chicks were challenged orally with 9 x 10(3) cfu/chick Salmonella Enteritidis and treated via oral gavage with 1 x 10(8) CB4Ø pfu/chick, 1.2 x 10(8) WT45Ø pfu/chick, or a combination of both, 1 h postchallenge. All treatments significantly reduced Salmonella Enteritidis recovered from cecal tonsils at 24 h as compared with untreated controls, but no significant differences were observed at 48 h following treatment. These data suggest that some bacteriophages can be efficacious in reducing SE colonization in poultry during a short period, but with the bacteriophages and methods presently tested, persistent reductions were not observed.