ABSTRACT Basa, Kristine Laurence D. May 2023. FUNGUS-MEDIATED SYNTHESIS OF SILVER NANOPARTICLES USING Colletotrichum spp. FROM INTECTIED TAMARIND LEAVES AND THEIRANTIBACTERIAL EFFICACY ON ENTERIC PATHOGENS FOUND IN BROILER CHICKEN, BACHELOR OF SCIENCE IN BIOLOGY. Pampanga State Agrieultural University Adviser: Prof. Ruth T. Libag, M.A.E.Chem. Recently, nanotechnology has emerged as a rapidly growing field with various biomedical applications. In this study, slver nanoparticles (AgNPs) were biosynthesized using the phytopathogenic fungus Colletotrichum spp. isolated from infected tamarind leaves, and its antibacterial action was assessed against enterie pathogens found in broiler chicken (E. coli, S. yphi, Shigella spp). The bio-reduction of AgNPs was characterized by visual inspection of color change (clear to brown), followed by the analysis of UV-visible spectroscopy which confirms the successful production of AgNPs (strong absorption peak monitored at 420nm). The SEM photomicrographs revealed that the nanoparticles were primarily composed of silver ions with sizes ranging from 66.96nm to 89,29nm. The antibacterial potential of fungus-mediated AgNPs was distinguished by performing the agar well diffusion method and determining minimum bactericidal concentration (MBC) and minimum inhibitory concentration (MIC) via resazurin and MTT assays, The antibacterial activity of AgNPs was found to outstandingly inhibit all bacterial strains in a concentration-dependent manner, with the largest mean zonal inhibition of 16.Imm at 6g. The MBC and MIC were found to be in the range of <0.5g to 0.5g, and 0.5g to lg, in both assays, respectively. The statistical analysis showed that there was a significant difference between the concentrations (p-value: 0.000) and no significant difference when compared to traditional antibiotics (p-value: >0.05). Finally, the biosynthesized AgNPs successfully inhibited the common pathogens found in chicken. Hereafter, its potential to control bacterial infections caused by multi-drug resistant pathogens could also be considered.