Comparative Evaluation of The Antimicrobial Potency of Four Traditional Nigerian Spices Against Selected Foodborne Pathogens

This study investigated the antimicrobial activities of Aframomum melegueta (alligator pepper), Syzygium aromaticum (clove), Tetrapleura tetraptera (aridan fruit), and Zingiber officinale (ginger) against selected Gram-positive and Gram-negative bacteria. Crude aqueous extracts of the spices were prepared and screened for antimicrobial activity using agar well diffusion assays. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by broth dilution methods. Test organisms included Staphylococcus aureus, Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa, Shigella dysenteriae , and Klebsiella spp. All experiments were performed in triplicate. Alligator pepper and clove exhibited the strongest antibacterial activity, with inhibition zones of up to 14.5 mm against S. aureus and 12.5 mm against P. aeruginosa. Their MIC values ranged from 12.5–25 mg/mL for Gram-positive bacteria and 25–50 mg/mL for Gram-negative bacteria, with MBC values generally one dilution higher. Ginger showed selective inhibition, strongly affecting S. aureus and S. dysenteriae , while E. coli and Klebsiella were less sensitive. Aridan fruit demonstrated weak inhibition across all tested organisms, with MIC ≥ 50 mg/mL and MBC > 100 mg/mL. Overall, Gram-positive organisms were more susceptible than Gram-negative bacteria, consistent with structural differences in cell wall composition.