ARS | Publication request: Effects of Short-Chain Nitrocompounds Against Campylobacter Jejuni and Campylobacter Coli in Vitro

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 31, 2006
Publication Date: March 20, 2007
Citation: Horrocks, S.M., Jung, Y., Huwe, J.K., Harvey, R.B., Ricke, S.C., Carstens, G.E., Callaway, T.R., Anderson, R.C., Ramlachan, N., Nisbet, D.J. 2007. Effects of short-chain nitrocompounds against Campylobacter jejuni and Campylobacter coli in vitro. Journal of Food Science. 72:M50-M55.

Interpretive Summary: Campylobacter are important human bacterial pathogens found in nearly all farm animals and are known to cause food poisoning of humans. In this study, we tested the killing activity of four nitrogen containing compounds (nitropropanol, nitroethanol, nitroethane and nitro-methylpropionate) against two different types of Campylobacter (C. jejuni and C. coli) during culture in microbiological media adjusted to simulate acidic, neutral or alkaline environments. Numbers of Campylobacter measured at different time intervals during the incubations decreased significantly in cultures containing the compounds but not in control cultures containing no compounds thus demonstrating that the compounds were effective in killing Campylobacter. The Campylobacter killing effect of most of the compounds was greatest under alkaline conditions. However, in the case of 2-nitro-methyl-propionate, survivability of C. jejuni was reduced most under acidic conditions. The effect of nitroethane and 2-nitro-1-propanol on Campylobacter naturally present in pig manure was also demonstrated thus indicating that these nitrocompounds can inhibit this pathogen in natural settings. These results provide a basis for further research to develop compounds as a new class of effective bacterial killing agents to reduce foodborne pathogens in animals. Ultimately, this research may help farmers and food processors produce safer and more wholesome food products for the American consumer.

Technical Abstract: Campylobacter is an important human pathogen that colonizes the gut of food producing animals. In this study, the effects of 2-nitro-1-propanol, 2-nitroethanol, nitroethane and 2-nitro-methyl-propionate (0, 10 and 20 mM) on growth of Campylobacter spp, were tested during culture in Bolton Broth adjusted to pH 5.6, 7.0 or 8.2 for C. jejuni and adjusted to pH 8.2 only for C. coli. Viable cell counts of samples taken at intervals during incubation revealed main effects (P < 0.05) of nitroethane, 2-nitro-1-propanol, 2-nitroethanol and 2-nitro-methyl-propionate on the survivability of C. jejuni. A marked effect of pH on the survivability of C. jejuni during incubation with all compounds was observed, with greater activity observed at pH 8.2 than at pH 5.6 or 7.0 for nitroethane, 2-nitro-1-propanol, 2-nitroethanol, but not for 2-nitro-methyl-propionate. In the case of 2-nitro-methyl-propionate, survivability of C. jejuni was reduced most at pH 5.6. Except for 2-nitro-methyl-propionate, which was ineffective, all nitrocompounds elicited similar effects on C. coli when cultured at pH 8.2. The effect of nitroethane and 2-nitro-1-propanol (10 mM) on wildtype Campylobacter was further investigated during incubation of a porcine fecal suspension. Campylobacter concentrations decreased more rapidly (P < 0.05) during incubation of porcine fecal suspensions supplemented with 2-nitro-1-propanol than unsupplemented control suspensions or suspensions supplemented with nitroethane thus reiterating the superior inhibitory effect of 2-nitro-1-propanol.