We analyzed raw ground beef testing data to determine whether a decrease in the rate of Escherichia coli O157:H7–positive raw ground beef samples has occurred since the inception of Food Safety and Inspection Service (U.S. Department of Agriculture) regulatory actions and microbiological testing concerning this commodity and pathogen. A main effects log-linear Poisson regression model was constructed to evaluate the association between fiscal year and the rate of E. coli O157: H7–positive raw ground beef samples while controlling for the effect of season for the subset of test results obtained from fiscal year (FY)2000 through FY2003. Rate ratios were used to compare the rate of E. coli O157:H7–positive raw ground beef samples between sequential years to identify year-to-year differences. Of the 26,521 raw ground beef samples tested from FY2000 through FY2003, 189 (0.71%) tested positive for E. coli O157:H7. Year-to-year comparisons identified a 50% reduction in the rate of positive ground beef samples from FY2002 to FY2003 when controlling for season (95% CI, 10 to 72% decrease; P = 0.02). This decrease was the only significant year-to-year change in the rate of E. coli O157:H7–positive raw ground beef samples but was consistent in samples obtained from both federally inspected establishments and retail outlets. We believe this decrease is attributed to specific regulatory actions by Food Safety and Inspection Service and subsequent actions implemented by the industry, with the goal of reducing E. coli O157:H7 adulteration of raw ground beef. Continued monitoring is necessary to confirm that the decrease in the rate of E. coli O157:H7 in raw ground beef samples we observed here represents the beginning of a sustained trend.

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