Submitted to: International Association of Milk Food and Environmental Sanitarians
Publication Type: Abstract Only
Publication Acceptance Date: February 11, 1999
Publication Date: N/A
Technical Abstract: Preharvest control of E. coli O157:H7 is a priority to the food industry. Since chlorate, an analog of nitrate, is reduced by respiratory nitrate reductases (enzymes possessed by E. coli and other enterobacteria) to cytotoxic chlorite, we conducted an experiment to see if chlorate could rid E. coli O157:H7 from ruminal contents, a reservoir of the pathogen. Bovine ruminal contents, inoculated with a novobiocin and nalidixic acid resistant E. coli O157:H7, were mixed (1:1) with phosphate buffer (pH 6.2 or 6.8) supplemented with cellobiose, glucose, soluble starch, and xylose (1% wt/vol each). These were incubated (39C) anaerobically with sodium chlorate as indicated. Escherichia coli O157:H7 concentrations (log10 cfu/ml), determined via colony counts (MacConkey's plus novobiocin and nalidixic acid; 25 and 20 ug/ml, respectively), declined slightly from initial levels (5.9) to 5.7 and 5.1 following 24 hr incubation of the cultures (pH 6.2 and 6.8, respectively) without added chlorate. Chlorate addition (1.25 or 5 mM) effected little the most probable number of total culturable anaerobes (ranging from 9.9 to 10.7 log10 cfu/ml) but markedly reduced the 24 hr concentrations of E. coli O157:H7 to </- 10 cfu/ml. Thus chlorate was bacteriocidal to E. coli O157:H7 but not to bacteria involved in normal gut function.