Antibacterial activities of Trichilia emetica seed and leaf crude extracts against selected foodborne pathogenic bacteria in Gambella Regional State, Southwest Ethiopia.

Abstract

Antibiotics are drugs intended to kill or inhibit the growth of bacteria. However, the increasing trend of antibiotic resistance by pathogenic bacteria is currently a public health concern. This necessitates a continuous and regular search for an alternative antibiotic source to diversify the potential antibacterial agents. The purpose of the study was to evaluate the antibacterial activity of Trichilia emetica leaf and seed extracts against foodborne pathogenic bacteria in Gambella regional state. A cross-sectional study design and lab-based experimental methods were used in this study. Moreover, ready-to-eat food samples of porridge, mandazi, and Nile tilapia were used to isolate and characterize the foodborne pathogens based on morphological and biochemical features; whereas leaf and seed of Trichilia emetica were collected, well dried, pulverized, and sequentially extracted by using petroleum ether, chloroform, acetone and methanol respectively, followed by phytochemical screening. Then food isolates for antibacterial activity were isolated from collected food samples. Antibacterial activities were evaluated using the standard agar diffusion technique. The results showed that out of 67 isolated colonies, a total of 19 isolates were identified, 9 from Nile tilapia, 5 from porridge, and 5 from Mandazi after the characterization based on biochemical and morphological features with 9 rods and 10 cocci shapes. It showed that there was a wide variation in the prevalence of Staphylococcus 10 (66.67%), Escherichia 4 (26.67%), Pseudomonas 3(20%), and Salmonella 2(13.33%) in each food sample, respectively. From antibacterial activity, methanol, and petroleum ether leaf extracts had shown significant activity against standard strains of S. aureus ATCC 25923 (16.6±74.73 and 18.6±74.16 mm) and food isolated Staphylococcus (19.00±2.52 & 19±2.65) and Escherichia (17.00±1.00) with (P<0.05), respectively. In comparison, petroleum ether, chloroform, and methanol seed extracts had the highest inhibitory effect against standard reference strains of S. typhi ATCC 13062 (17.6±71.53), S. aureus ATCC 25923 (18.00±1.00mm) and E. coli ATCC 25922 (20.33±1.53); while exhibited activity against food isolated Escherichia (17.00±1.00) respectively. The MIC against food and standard isolates ranged from 12.5 to 25 mg/ml. Among the plant secondary metabolites, flavonoids, tannins, saponins, terpenoids, and steroids were found in both the seed and the leaf. Generally, methanol extract was the most effective in all cases. The study concluded that leaf and seed of T.emetica had the antibacterial properties. Therefore, in-vivo efficacy of leaf and seed extracts is needed for further research.