EVALUATION OF ANTIBACTERIAL ACTIVITY OF TRICHILIA DREGEANA SOND (MELIACEAE) CRUDE EXTRACTS AGAINST GRAM-POSITIVE AND GRAM-NEGATIVE BACTERIA

Abstract

Medicinal plants have been playing a crucial role in drug discovery and development against infectious diseases. The antibacterial activity of methanol crude extract of traditionally used Trichilia dregeana Sond was evaluated against common bacterial pathogens. Agar well diffusion and broth dilution assays were used to evaluate the antimicrobial activity and MIC of crude methanol plant extracts. The methanol crude extract of Trichilia dregeana Sond showed promising antibacterial activity against all tested bacterial isolates. A significant difference (p < 0.05) was observed in susceptibility among Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa species isolates. A higher mean susceptibility or inhibition zone diameter to crude extracts was observed in Escherichia coli (19.6 ± 5.9 mm) and Pseudomonas aeruginosa (18.4 ± 5.9 mm) compared to Staphylococcus aureus isolates. Significant differences were also observed in the susceptibility of tested bacterial isolates at different concentrations of crude extracts. A higher inhibition zone diameter was recorded in Pseudomonas aeruginosa (27.2 ± 1.5 mm), followed by Escherichia coli (25.2 ± 1.5 mm), and Staphylococcus aureus (21.1 ± 1.4 mm) at a concentration of 100 mg/mL. A comparable inhibition zone of crude extracts was observed with that of the positive control at 100 mg/mL concentration against Staphylococcus aureus and Escherichia coli isolates. The findings indicated that bacterial growth inhibition increased as the concentration of the crude extracts increased. All tested pathogenic bacteria species (gram-positive and gram-negative) were susceptible to plant leaf extract, even at lower levels of concentration. This showed the plant extracts’ broad-spectrum activity against both gram-positive and gram-negative bacteria. The methanol crude extract of plants is an effective antibacterial agent for treating bacterial infections since the extract showed significant antibacterial potency comparable with that of the standard antibiotic disk. The findings are promising and encourage further investigation of the crude extracts’ phytochemical, toxicological, and pharmacological aspects to support their potential rational use in antimicrobial therapy.