In vitro assessment of antibacterial effect of crude extracts of Tetradenia riparia leaves on pathogenic Escherichia coli isolated from chicken samples submitted to Central Diagnostic Laboratory,Makerere University.

Abstract

The poultry industry faces significant losses due to bacterial diseases, notably infections caused by Avian Pathogenic Escherichia coli (APEC), which contribute to high morbidity and mortality. With rising antimicrobial resistance (AMR), there is growing interest in plant-based alternatives such as Tetradenia riparia, a medicinal plant traditionally used for various infections. This study assessed the qualitative phytochemical composition and antibacterial activity of crude aqueous and ethanoic leaf extracts of T. riparia against pathogenic E. coli isolated from chicken samples submitted for diagnosis at Central Diagnostic laboratory. Fresh leaves of T. riparia were collected, air-dried in a shade, and ground into powder before extraction using water and ethanol as solvents. Qualitative phytochemical screening was conducted using standard methods to identify secondary metabolites. Archived pathogenic E. coli samples were retrieved and sub-cultured from the microbiology unit of Central Diagnostic Laboratory (CDL), College of Veterinary Medicine, Animal Resources and Biosecurity (COVAB), Makerere University. The antibacterial activity of the extracts was determined using the agar well diffusion method at concentrations ranging from 50 mg/ml to 500 mg/ml, with zone of inhibition (ZOI) measured in millimeters. Phytochemical analysis revealed the presence of saponins, tannins, reducing compounds, alkaloids, anthracenocides, coumarins, flavonoids, and steroid glycosides in both extracts, while anthocyanocides were absent. High levels of saponins and reducing compounds were present in both extracts, whereas alkaloids and steroid glycosides were more abundant in the ethanoic extract. Antibacterial testing demonstrated a concentration-dependent activity, with no inhibition at 50 mg/ml and maximum activity at 500 mg/ml, where the ethanoic extract (mean=13.6±0.05mm) slightly outperformed the aqueous extract (mean=12.7±0.05 mm). T. riparia leaves contain multiple bioactive compounds with antibacterial properties against pathogenic E. coli. However, the ethanoic extracts of concentrations 125mg/ml, 250mg/ml and 500mg/ml showed a superior efficacy

over the aqueous extract, and the observed differences were statistically significant with p- values 0.045, 0.032, 0.028 respectively at 5% level of significance. The plant shows potential

as a natural antibacterial agent for poultry disease control, warranting further in vivo efficacy and safety studies.