In vitro and in vivo efficacies of amlodipine against <Emphasis Type="Italic">Listeria monocytogenes</Emphasis>

Listeria monocytogenes causes suppurative gastritis in BALB/c mice. We investigated the effect of the antihypertensive drug amlodipine (Aml) on the growth of L. monocytogenes in vitro and in vivo. Aml showed noteworthy inhibitory action (minimum inhibitory concentration, MIC₉₀ 32 μg/ml) against Listeria strains and demonstrated cidal (minimum bactericidal concentration, MBC 64 μg/ml) activity. Aml administered orally at 2.5 μg/g in female BALB/c mice for 7 days, commencing 4 days before oral challenge (1 × 10⁸ CFU/ml with L. monocytogenes ATCC 51774), significantly reduced bacterial counts in the stomach (P < 0.01), liver (P < 0.01), and spleen (P < 0.05), and decreased (P < 0.05) gastric lesions, neutrophilic infiltration, edema, vascular degeneration, and necrosis of gastric tissues. It caused the down-regulation of expression of inflammatory cytokines (IFN-γ, IL-1β, and TNF-α) compared to drug-free control. Aml may be used in the presence of an antibiotic as adjunct therapy that boosts the host immunity against Listeria. Further, QSAR studies might contribute in manipulating it as a lead compound for the synthesis of new, more effective non-antibiotics (helper compounds), perhaps devoid of side-effects, that could be recommended as compassionate therapy for listeriosis.