U.S. beef slaughter facilities are required to use a carcass intervention treatment to reduce contamination by Escherichia coli O157 : H7. Very small beef slaughter operators generally are unable to carry out challenge studies to validate intervention treatment effectiveness, and in-plant pathogen challenge studies are not permitted. The objective of this study was to evaluate the effectiveness' measured by decreases in generic E. coli, coliforms, Enterobacteriaceae, and aerobic plate count, of intervention treatments used at very small beef slaughter facilities in Wisconsin. Over a 9-mo period, 265 head of beef were sampled at 22 very small beef slaughter facilities before and after the intervention treatment. The interventions studied were dry-aging, low-pressure hot-water spray, high-pressure hot-water spray, 2.5% acetic acid spray, and Fresh Bloom (TM) (a mix of citric acid, ascorbic acid, and erythorbic acid) spray. Sprays were applied using a hand-held nozzle (hot water) or a pump-type sprayer (acid). There was no significant difference (P > 0.10) between intervention treatments and all treatments caused significant reductions (P < 0. 10) in indicator organisms. Ranges in average reductions for generic E. coli, coliforms, and Enterobacteriaceae among the treatments were 0.6 to 2.0 log CFU/cm(3), 0.7 to 2.2 log CFU/cm(2), and 0.4 to 2.2 log CFU/cm(2), respectively. For all treatments, rapid decreases in cooler temperature and relative humidity significantly affected indicator reduction, and for hot-water washing, increasing spray time led to significantly greater reductions. Further studies using actual or simulated very-small-plant intervention treatments directly against E. coli O157,117 would provide additional validation of treatment efficacy,
