Effect of combined piperine and amoxicillin as an efflux pump inhibitor for metal-tolerant and antibiotic - resistant E. coli in broilers.

This study investigated the effects of combining piperine, an efflux pump inhibitor, with amoxicillin in broilers infected with resistant E. coli O125, evaluating antibacterial efficacy, efflux-associated gene expression, pharmacokinetics, and residue depletion. In vitro, amoxicillin and piperine minimum inhibitory concentrations (MICs) were 32 and 5 µg/mL, respectively, with a synergistic fractional inhibitory concentration (FIC) index of 0.2518. Piperine toxicity and oxidative stress markers were also assessed. Two hundred twenty-five-day-old chicks were divided into five groups: negative and positive controls, and three infected groups treated orally for five days with amoxicillin, piperine, or their combination. E. coli counts, efflux gene expression, and heavy metal concentrations were evaluated at multiple time points. Serum and tissue drug concentrations were quantified using validated HPLC, followed by compartmental pharmacokinetic and residue depletion analyses. Dietary piperine (100 mg/kg) was well-tolerated and improved antioxidant status. Co-administration with amoxicillin reduced mean E. coli counts to 2.2 log10 CFU/g and downregulated efflux genes 0.4-0.5-fold change. Amoxicillin followed two-compartment kinetics, while piperine followed a one-compartment model. Piperine significantly increased amoxicillin maximum plasma concentration (Cmax) and area under the curve (AUC), while decreasing clearance. Furthermore, piperine enhanced amoxicillin systemic exposure and prolonged tissue persistence. From a regulatory standpoint, this combination requires an extended withdrawal period of 5 days post-cessation compared to 3 days for amoxicillin alone, to ensure compliance with amoxicillin maximum residue limits (MRLs). Low concentrations of zinc, copper, and cadmium were detected across tissues. These findings suggest piperine enhances amoxicillin efficacy through resistance-modulating and pharmacokinetic mechanisms.