Evaluation of Antimicrobial Potential of Medicinal Plant Extracts Against Multidrug-Resistant Bacteria Isolated from Pharmaceutical-Contaminated Water in Kano State, Nigeria

Abstract

Pharmaceutical wastewater discharged into open drainage channels around hospitals and pharmaceutical facilities may serve as an important reservoir of multidrug-resistant bacteria and other contaminants of public health concern. This study evaluated the antimicrobial potential of selected medicinal plant extracts against multidrug-resistant bacterial isolates recovered from pharmaceutical-contaminated drainage water in Kano State, Nigeria. Wastewater samples were collected from open drains located outside Aminu Kano Teaching Hospital, Murtala Mohammed Specialist Hospital, Sabon Gari Pharmaceutical Market, and pharmaceutical facilities in Sharada Industrial Estate. Physicochemical parameters of the wastewater were determined using standard methods. Bacteria were isolated, identified by biochemical characterisation and 16S rRNA confirmation, and tested for antibiotic susceptibility using the Kirby–Bauer disc diffusion method. Aqueous and ethanolic extracts of Azadirachta indica, Moringa oleifera, Vernonia amygdalina, Psidium guajava, Allium sativum, and Zingiber officinale were prepared and evaluated against the multidrug-resistant isolates. The wastewater samples showed elevated levels of electrical conductivity (1215–1582 µS/cm), biochemical oxygen demand (48.7–73.5 mg/L), and chemical oxygen demand (108.5–152.3 mg/L), exceeding recommended limits. Escherichia coli was the most prevalent bacterial isolate, accounting for 29.8% of all isolates, followed by Staphylococcus aureus (21.1%) and Pseudomonas aeruginosa (18.5%). Pseudomonas aeruginosa exhibited the highest multidrug resistance rate (71.2%), with marked resistance to ampicillin (92.7%) and tetracycline (75.6%). Among the plant extracts, ethanolic extracts were more active than aqueous extracts. Garlic ethanolic extract showed the strongest antimicrobial activity, producing inhibition zones of 26.8 ± 1.7 mm against Escherichia coli, 29.4 ± 1.6 mm against Staphylococcus aureus, and 23.1 ± 1.4 mm against Pseudomonas aeruginosa. Guava leaf ethanolic extract also demonstrated substantial antibacterial activity. The minimum inhibitory concentration of garlic extract ranged from 6.25 to 25 mg/mL, while the minimum bactericidal concentration ranged from 12.5 to 50 mg/mL. The findings indicate that pharmaceutical-contaminated drainage water in Kano State contains highly resistant bacteria and that selected medicinal plants, particularly Allium sativum and Psidium guajava, possess strong antimicrobial activity against these organisms. The study suggests that these plants may provide low-cost alternative agents for the control of multidrug-resistant bacteria associated with environmental contamination.pharmaceutical wastewater