Location: Food and Feed Safety ResearchTitle: Antimicrobial activity of select anti-methanogenic nitro- and thio-containing compounds
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 11/30/2016
Publication Date: N/A
Technical Abstract: New technologies are needed to help livestock producers maintain optimal health and wellbeing in their animals while minimizing risks of propagating and disseminating antimicrobial resistant bacteria to humans or other animals. Where possible, these interventions should contribute to the efficiency and profitability of animal production so as to avoid passing higher costs on to the consumer. Methane production within the rumen results in the loss of 2-12% of the gross energy consumed by the host, costing the U.S. cattle feeding industry as much as $700,000/day or more. Rumen methanogenesis also contributes 20% of the U.S. emission of this greenhouse gas. Presently, we examined the antimicrobial activity of several potential anti-methanogenic chemicals to see if their applications may be combined to be more economically acceptable for producers. When tested against anaerobically-grown (in tryptic soy broth) pure cultures of Salmonella Typhimurium (ST) and Escherichia coli O157:H7 (EC), the potent methane inhibitor ethyl nitroacetate (9 mM) decreased (P < 0.05) mean specific growth rates by 26 and 36%, respectively, compared to that of controls (0.481 +/- 0.05 and 0.357 +/- 0.02, respectively). Ethyl nitroacetate was bacteriostatic rather than bactericidal, as evidenced by nearly equivalent (P > 0.05) maximum optical densities (0.40 +/- 0.01 and 0.39 +/- 0.03 at 600 nm, respectively) recorded after 24-h incubation (39 degrees C). The methane inhibitors nitroethane and 3-nitro-1-propionic acid were ineffective in inhibiting ST or EC. When tested likewise, 9 mM 6,8-dithiotic acid (common name lipoic acid) decreased (P < 0.05) mean specific growth rates and maximal optical densities of ST by 98 and 65% and of EC by 93% and 59%, respectively. Mechanistically, evidence indicates that ethyl nitroacetate disrupts hydrogen transfer reactions, whereas the antimicrobial effect of lipoic acid, a player in one carbon compound metabolism, may be mediated by pH.