Role of Metabolic Intermediates in the Inhibition of Salmonella typhimurium and Salmonella enteritidis by Veillonella

Abstract

A Veillonella sp. was isolated from the cecal contents of adult chickens. The Veillonella was grown on an agar medium supplemented with 200mM of lactate, pyruvate, fumarate, or succinate and adjusted to a pH of 6.7, 6.5, 6.3, 6.1, 5.9, or 5.7. No metabolites were added to the control media, but it was adjusted to the same pH levels as the supplemented media. The agar medium on which the Veillonella was grown was overlaid with fresh agar medium. Cultures of Salmonella typhimurium or Salmonella enteritidis were spread on the surface of the agar overlay, and the plates were incubated at 37°C for 14–18 h. Veillonella did not inhibit the growth of either salmonellae on any of the control or pyruvate medium. Veillonella did inhibit the growth of both salmonellae on lactate medium that had been adjusted to pH 6.3, 6.1, or 5.9 and on succinate medium that had been adjusted to pH 5.7. Veillonella also inhibited the growth of S. typhimurium on fumarate medium that had been adjusted to pH 6.7, 6.5, 6.3, 6.1, or 5.9; and it inhibited the growth of S. enteritidis on fumarate medium that had been adjusted to pH 6.7, 6.5, 6.3, or 6.1. Inhibition on lactate agar was correlated with the production of acetate and propionate by Veillonella and residual lactate in the medium; inhibition on fumarate agar was correlated with the production of propionate and lactate by Veillonella; and inhibition on succinate agar was correlated to the production of propionate at low pH levels. The findings indicate that anaerobic bacteria that produce these metabolic intermediates and anaerobic bacteria that can convert the intermediates to volatile fatty acids may be important components of probiotic cultures that can be provided to chicks to reduce colonization by salmonellae.