In vitro interaction between essential oil compounds and halquinol against zoonotic pathogenic bacteria

Abstract

The use of growth-promoting antibiotics has led to an increase in antimicrobial resistance; therefore, the search for new alternatives is essential. As many producers are afraid of applying new technologies, the association between conventional and new methods is an opportunity to introduce innovative approaches. The objective of this research was to evaluate the interaction between halquinol and allyl isothiocyanate (AITC), cinnamaldehyde (CIN), and carvacrol (CA). The minimum inhibitory concentrations were evaluated against Salmonella and Escherichia coli, in addition to their fractional inhibitory concentration index (FICindex), the potential for antimicrobial resistance, and the reversal of halquinol resistance. The compounds were effective when used isolated, with an emphasis on AITC, effective in concentrations between 31.25 and 500 μL/L. Halquinol was effective in the range from 18.75 to 600 μg/mL, working within the range recommended by the manufacturer (30–60 ppm) for most bacteria. The FICindex has shown that the combinations of halquinol with CIN and CA presented mostly synergistic and additive effects. In sublethal exposures, prolonged exposure to EOC mainly led to the potentiation of their effects, and exposure to halquinol led to resistance, increasing its inhibitory concentration by approximately 10 times. Resistance reversal tests showed that AITC and CIN have the potential to minimize resistance to halquinol in vitro.