Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 15, 2004
Publication Date: November 4, 2004
Citation: McReynolds, J.L., Byrd II, J.A., Moore, R.W., Anderson, R.C., Poole, T.L., Edrington, T.S., Kubena, L.F., Nisbet, D.J. 2004. Utilization of the nitrate reductase enzymatic pathway to reduce enteric pathogens in chickens. Poultry Science. 83:1857-1860. Interpretive Summary: Salmonella bacteria can cause illness and death in humans consuming contaminated poultry products. Poultry meat may become contaminated with Salmonella during the slaughter process when the birds are going through the processing plant. Treatment with a bacterial culture (competitive exclusion culture), that contains normal beneficial bacteria from the intestinal tract of healthy adult chickens, has been shown to protect newly hatched chicks from Salmonella. Salmonella bacteria possess an enzyme that converts chlorate to chlorite that will build-up inside the bacteria causing it to die. In this study, we looked at combining an experimental chlorate product and treating chicks with the beneficial bacteria for their effectiveness to reduce Salmonella. When chicks were treated with these products, only a few of the beneficial bacteria were sensitive to the chlorate product but most of the Salmonella were killed. This finding is important because it will aid in designing management practices to reduce or prevent contamination of meat and machinery by Salmonella bacteria.
Technical Abstract: Poultry are frequently implicated as a vehicle for human salmonellosis. Previous reports have shown that some bacteria, including Salmonella, utilize a dissimilatory nitrate reductase enzyme (NR) in anaerobic environments. This enzyme reduces nitrate to nitrite and also reduces chlorate to cytotoxic chlorite. The present investigations were performed to evaluate the susceptibility of a competitive exclusion culture (CE) to the experimental chlorate product (ECP). A commercial CE product was evaluated for its nitrate reductase activity and chlorate sensitivity. The 29 constituent bacteria of the CE culture, of which 15 strains are facultative and 14 are obligate anaerobes were individually cultured in Viende LeVure-broth containing 5 mM sodium nitrate or 10 mM sodium chlorate. Bacterial growth (OD 625 nm) was measured and 1 mL aliquots were removed at intervals for colorimetric determination of nitrate. Of the 15 different facultative strains, 11 had slight NR activity, 3 had moderate NR utilization; the remaining were NR negative (with slight and moderate NR utilization: >0.1 to < 1.0 mM and > 1.0 mM nitrate utilized within 6 h, respectively). Of the obligate anaerobes evaluated, 3 exhibited slight utilization and the remaining were NR negative. Of the total NR positives, fifty percent were chlorate sensitive, as evidenced by marked inhibitions in growth over the 24 h incubation period. In vivo studies utilizing both products (CE and ECP) in a horizontal transmission challenge model (seeders + contacts) showed significant reductions in Salmonella from 5.37 to 1.76 log10 cfu/g and 3.94 to .07 log10 cfu/g, respectively. Although some of the CE bacteria are affected by ECP as seen in the in vitro data; these are apparently not essential for CE function as the combined affect of the CE culture and a ECP are effective in killing these foodborne pathogens.