Submitted to: Proceedings of the International Symposium on Digestive Physiology in Pigs
Publication Type: Proceedings
Publication Acceptance Date: September 5, 2000
Publication Date: February 1, 2001
Interpretive Summary: Salmonella are important disease causing bacteria found throughout the world. These bacteria cause disease in pigs and can contaminate pork products sold to consumers. Consequently, strategies are sought to rid these bacteria from pigs. We conducted a study to determine if a new use for a well known chemical, chlorate, could selectively kill Salmonella, but not potentially beneficial bacteria, within the pig gut. In this experiment, pigs were experimentally infected with Salmonella typhimurium and then were treated with either no or two moderate concentrations of sodium chlorate. At the end of the experiment, we found that chlorate treatment reduced gut concentrations of Salmonella typhimurium more than 10-fold, from about 500 Salmonella cells per gram of gut contents to less than 40 Salmonella cells per gram of gut contents. The chlorate treatment did not decrease the numbers of potentially beneficial bacteria. These results suggest that chlorate may be a useful treatment to reduce Salmonella infections in pigs and may thus reduce economic losses incurred by pig producers. Ultimately, chlorate may reduce the risk of pork products becoming contaminated by these food borne pathogens.
Technical Abstract: Salmonella remain an important cause of enteric disease in many regions of the world. Salmonella possess respiratory nitrate reductase activity that also catalyzes the intracellular reduction of chlorate to cytotoxic chlorite. Because most gut anaerobes lack respiratory nitrate reductase, we conducted a study to determine if chlorate may selectively kill Salmonella but not potentially beneficial anaerobes within the pig gut. Weaned 26 to 29 day old pigs were orally infected with 10**8 colony forming units (CFU) of Salmonella typhimurium (ST). The pigs were randomly placed into three treatment groups (15 pigs/group). Treatments were administered at 8 and again at 16 hr post ST challenge via oral gavage (10 ml) of 0, 100 or 200 mM sodium chlorate solution, each corresponding to placebo, 1X or 2X treatment, respectively. Five pigs per group were euthanized at 8 hr intervals following the last treatment and specimens collected by necropsy were cultured for ST and total culturable anaerobes. No significant differences in proportions of pigs yielding ST-positive ileocolic lymph nodes (0 to 80%) or cecal contents (60 to 100%) were observed. Mean cecal concentrations of ST (log base 10 CFU/g) were significantly less (P < 0.05) in the 1X and 2X groups (1.5 and 1.3, respectively) than in the placebo group (2.7). There was no significant time after treatment effect on cecal ST concentrations and at no time were Most Probable Numbers of total culturable anaerobes affected by any treatment (values ranged from 10.6 to 11.5 log base 10 cells/g). These results show that chlorate treatment reduced ST colonization within the pig gut without reducing concentrations of potentially beneficial anaerobes.