title: Bactericidal effect of sodium chlorate on Escherichia coli O157:H7 and Salmonella typhimurium DT104 in rumen contents in vitro.
abstract: Escherichia coli O157:H7 and Salmonella Typhimurium DT104 are important foodborne pathogens affecting the beef and dairy industries and strategies are sought to rid these organisms from cattle at slaughter. Both pathogens possess respiratory nitrate reductase that also reduces chlorate to the lethal chlorite ion. Because most anaerobes lack respiratory nitrate reductase, we hypothesized that chlorate may selectively kill E. coli O157:H7 and Salmonella Typhimurium DT104 but not potentially beneficial anaerobes. In support of this hypothesis, we found that concentrations of E. coli O157:H7 and Salmonella Typhimurium DT104 were reduced from approximately 1,000,000 colony forming units (CFU) to below our level of detection (< or = 10 CFU) following in vitro incubation (24 h) in buffered ruminal contents (pH 6.8) containing 5 mM added chlorate. In contrast, chlorate had little effect on the most probable number (mean +/- SD) of total culturable anaerobes (ranging from 9.9 +/- 0.72 to 10.7 +/- 0.01 log10 cells/ml). Thus, chlorate was bactericidal to E. coli O157:H7 and Salmonella Typhimurium DT104 but not to potentially beneficial bacteria. The bactericidal effect of chlorate was concentration dependent (less at 1.25 mM) and markedly affected by pH (more bactericidal at pH 6.8 than pH 5.6).
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, Southern Plains Agricultural Research Center, College Station, Texas 77845, USA. anderson@ffsru.tamu.edu
authors.forename: R C
authors.initials: RC
authors.lastname: Anderson
authors.forename: S A
authors.initials: SA
authors.lastname: Buckley
authors.forename: L F
authors.initials: LF
authors.lastname: Kubena
authors.forename: L H
authors.initials: LH
authors.lastname: Stanker
authors.forename: R B
authors.initials: RB
authors.lastname: Harvey
authors.forename: D J
authors.initials: DJ
authors.lastname: Nisbet
mesh_terms: D000818:Animals; D002417:Cattle; D002704:Chlorates / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D019453:Escherichia coli O157 / Q000187:drug effects* / Q000254:growth & development; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D050901:Nitrate Reductase; D009565:Nitrate Reductases / Q000378:metabolism; D012417:Rumen / Q000382:microbiology*; D012486:Salmonella typhimurium / Q000187:drug effects* / Q000254:growth & development
chemical_list: D002704:Chlorates; D009565:Nitrate Reductases; D050901:Nitrate Reductase; C032706:sodium chlorate