In-vitro Antimicrobial Potential of Methanolic Leaf Extract of Azadirachta indica on Bacterial Isolates from Apparently Healthy Dogs

The objective of this research work was to determine whether neem leaf (Azadiracha indica) possesses antibiotic activity, with potential bacteriostatic and bactericidal effects on bacteria isolated from apparently healthy dogs. The leaves were washed, air-dried and ground. Using Soxhlet extractor, the extract was collected and stored in the refrigerator until ready for use. The phytochemical property of this plant was screened, after which the antimicrobial activity was tested. The stored extracts were reconstituted into four different folds of concentration. Agar well diffusion method was employed with a Mueller-Hinton agar. Staphylococcus aureus and Escherichia coli were isolated from dogs. Test isolates were prepared in peptone water and incubated for 2-3 hours at 37 °C. The prepared test organisms were spread individually on the Mueller-Hinton agar using a glass rod, and with a 6mm cork borer, 4 wells were made on each plate, and each well containing four drops of the different concentrations of extracts reconstituted and the plates were incubated at 37 °C for 24 hours. The result was estimated based on the zone of inhibition produced at different concentrations and measured in millimetres. Staphylococcus aureus and Escherichia coli at 100mg/ml and 200mg/ml, respectively, showed remarkable zones of inhibition. Staphylococcus aureus produced zones of inhibition at 4.2 mm and 9.4 mm, while Escherichia coli produced 3.0mm and 7.0mm. The result of the phytochemical analysis showed the presence of saponin, phytate, glycosides, alkaloids, flavonoids and tannins. This study showed that Azadiracha indica has an antimicrobial effect on Staphylococcus aureus and Escherichia coli, based on the concentration applied and this may be as a result of the phytochemical constituents found in them.