Antimicrobial Effects of Aqueous Bark Extracts of Khaya senegalensis, Azadirachta indica and Euclyptus camaldulensis against Different Bacterial Pathogens

Abstract

Introduction: aqueous bark preparations of Khaya senegalensis, Azadirachta indica, and Eucalyptus camaldulensis are widely employed in traditional medicine for the management of microbial infections in both humans and animals. The present work aimed to investigate the antibacterial potential of these plant extracts against selected Gram-positive bacteria (Staphylococcus aureus and Staphylococcus epidermidis) and Gram-negative bacteria (Klebsiella pneumoniae, Escherichia coli, and Salmonella dublin).
Methods: bark materials were extracted with water to obtain concentrations equivalent to 20 g, 40 g, and 50 g per 100 mL. Antibacterial activity was evaluated using the agar well diffusion technique at the Microbiology Laboratory, Faculty of Veterinary Medicine, University of Khartoum. Bacterial susceptibility was determined by measuring inhibition zone diameters around the wells.
Results: all tested aqueous extracts demonstrated inhibitory effects against the examined bacterial strains at every tested concentration. Antibacterial activity increased with rising concentration, with the maximum effect observed at 0.5 mg/mL. At this level, inhibition zones against Staphylococcus aureus measured 3.7 ± 0.52 cm for Khaya senegalensis, 3.0 ± 0.24 cm for Azadirachta indica, and 2.8 ± 0.57 cm for Eucalyptus camaldulensis.
Conclusion: the findings indicate that bark-derived aqueous extracts from the three studied species possess notable antibacterial activity against both Gram-positive and Gram-negative pathogens, particularly at higher concentrations. These results support their traditional use and suggest the need for further investigations involving other plant organs—such as leaves, fruits, and roots—tested across a wider range of concentrations.