Hika Waktole (PhD)Tadelech Yilma2026-07-032026-07-032026https://etd.aau.edu.et/handle/123456789/8606It is evident that Antimicrobial resistance (AMR) is a growing health challenge affecting humans, animals, and the environment. Current practices involving extensive antimicrobial use and intensive poultry production systems favour the creation of important reservoirs of resistant bacteria, particularly to tetracyclines and β-lactams groups of antibiotics. However, previous studies assessing antimicrobial-resistant bacteria across poultry, environmental, and human interfaces remain limited in Ethiopia. This study aimed to investigate tetracycline- and β-lactamresistant Escherichia coli (E. coli) and Enterococcus faecalis (E. faecalis) across the poultry– environment–human interface in Bishoftu, Ethiopia. Accordingly, a cross-sectional study was conducted from November 2025 to June 2026 on 70 selected commercial poultry farms in Bishoftu, Ethiopia. A total of 210 cloacal, litter, and farm worker hand swab samples were collected. The isolation and identification of the bacteria were performed using standard culture, biochemical, and molecular confirmation methods. Antimicrobial susceptibility test was conducted using the Kirby–Bauer disk diffusion method following CLSI guidelines. PCR test was used to detect the tetM, blaTEM, stx2, and ddl genes in the isolated bacteria. The findings of this study disclosed that E. coli and E. faecalis were isolated from 31.0% (65/210) and 44.8% (94/210) of the samples, respectively. The occurrence of E. coli ranged from 30.0% to 31.4%, while E. faecalis ranged from 38.6% to 50.0% across the examined samples. High resistance of E. coli isolates was observed against tetracycline (91.5%) and ampicillin (72.3%), whereas all recovered E. coli strains remained responsive to gentamicin, implying 100% susceptibility. Similarly, multidrug resistance was detected in 19.1% of E. coli and 85.1 % of E. faecalis isolates. This study also revealed molecular analysis results that confirmed the presence of tetM and blaTEM resistance genes among resistant isolates of the sample domains. The stx2 virulence gene was also detected among selected E. coli isolates. Findings of this study demonstrated that tetracycline and β- actam-resistant E.coli and E. faecalis were detected in poultry, litter and human samples, indicating their distribution across the poultry production system. The presence of resistant isolates in poultry litter indicates its potential role as a reservoir for antimicrobial resistance. Those findings highlight the importance of strengthening antimicrobial stewardship, farm biosecurity, and integrated surveillance of AMR to reduce dissemination of AMR within the One Health continuumen-USAntimicrobial resistance (AMR)E. coliE. faecalisEthiopiaOne HealthPoultryThesis