Evaluation of a Product Intended for Microbiological Control in Animal Production, and Its Combination With Halquinol

Antimicrobial resistance is an increasingly pressing global concern, with one of its contributing factors being the use of subtherapeutic doses of antibiotics in animal production for zootechnical purposes. Halquinol (HA) remains one of the few compounds still permitted in certain regions; however, the development of alternative solutions is imperative. This study evaluated the in vitro effects of a formulation composed of essential oils and organic acids against Salmonella and Escherichia coli as well as its interaction with HA. The formulation demonstrated both inhibitory and bactericidal activity against the bacteria, with effective concentrations ranging from 2.0 to 8.0 mL/L. In contrast, HA exhibited solely bacteriostatic effects, with minimum inhibitory concentrations ranging from 37.5 to 300 μg/mL. When used in combination, the compounds predominantly resulted in additive or indifferent interactions: 51.35% of the assays showed additive effects, 43.24% exhibited no interaction, and only 5.41% demonstrated antagonistic interactions. Importantly, the formulation did not induce bacterial resistance or adaptation following sublethal exposure. Conversely, sublethal exposure to HA led to an approximately tenfold increase in its bacteriostatic dose. Moreover, the formulation showed potential to mitigate resistance induced by sublethal HA exposure. In a simulated swine digestion, the combination of the formulation with HA was particularly effective against E. coli , with the co‐administration reducing the required concentrations of the individual compounds to achieve sustained bacterial suppression throughout the digestive process. Based on these findings, the tested formulation demonstrates promising potential for bacterial control and may be used in combination with HA to reduce its required dosage.