Influence of pH and oxygen levels on the antimicrobial efficacy of acetic acid against Salmonella Typhimurium.

Abstract

Aims: This study aimed to evaluate the antibacterial effects of varying acetic acid (AA) concentrations on Salmonella Typhimurium under chicken gastrointestinal tract (GIT)-like conditions, focusing on the influence of pH and oxygen availability.

Methods and results: Experiments were conducted under aerobic and oxygen-limited conditions using culture media adjusted to typical poultry GIT pH values. Growth was monitored via spectrophotometry, and minimum inhibitory concentrations (MICs) were determined after 48 h. Bacterial growth kinetics were modeled using Weibull and secondary models. Results showed that under limited oxygen at pH 4.5, S. Typhimurium demonstrated growth without AA. At pH 5.5 and 6.5, the MICs were 3.44 mM (0.53 mM undissociated) and 330 mM (5.9 mM undissociated), respectively. In aerobic conditions, MICs ranged from 4 mM to 473 mM depending on pH. Notably, at pH 5.5, MICs under oxygen-limited conditions were three times lower than those under aerobic conditions, indicating enhanced inhibitory effects of AA in low-oxygen environments.

Conclusions: This study highlights the pH- and oxygen-dependent efficacy of AA against S. Typhimurium, with significantly improved antibacterial activity under oxygen-limited conditions. The developed models provide a predictive framework for understanding S. Typhimurium responses to AA in poultry GIT environments, offering insights for optimizing feed additives to mitigate Salmonella colonization.