Antimicrobial Properties of Garlic (Allium sativum) Extract Against Multi-Drug Resistant Bacteria Isolated in Port Harcourt

Garlic, Allium sativum, has a centuries-long history of medicinal use, and its active compound allicin has demonstrated broad-spectrum antimicrobial activity in multiple experimental studies. This laboratory-based study evaluated the in-vitro antimicrobial activity of aqueous and ethanolic garlic extracts against selected multi-drug resistant (MDR) clinical bacterial isolates obtained from the diagnostic laboratory of Rivers State University Teaching Hospital, Port Harcourt, Rivers State, in the South South geopolitical zone of Nigeria. MDR isolates including MRSA, ESBL-producing E. coli, MDR Pseudomonas aeruginosa, and MDR Klebsiella pneumoniae were tested. Extract concentrations of 25, 50, 100, 200, and 400 mg per mL were prepared and activity was assessed by agar well diffusion. MIC and MBC were determined. The ethanolic extract exhibited greater antimicrobial activity than the aqueous extract across all isolates. MRSA and ESBL E. coli showed the highest zones of inhibition at 400 mg per mL, measuring 18 mm and 15 mm respectively. P. aeruginosa demonstrated the least susceptibility. Phytochemical analysis confirmed allicin, flavonoids, and organosulfur compounds as likely active constituents. These results support further pharmacological characterization and clinical translation of garlic-derived antimicrobials, particularly in the context of rising MDR infections in Nigeria. Keywords: Allium sativum, garlic extract, multi-drug resistance, antimicrobial activity, Port Harcourt.