Antimicrobial resistance (AMR) occurs when microorganisms fail to respond to the therapeutic onslaught of antibiotics. Extended-spectrum beta-lactamase (ESBL) and AmpC enzymes are important AMR mechanisms that erode the efficacy of important antibiotics. Here, we report on the detection and susceptibility of ESBL- and AmpC-producing bacteria from livestock and poultry environments. Bacteriological and molecular biology tools were used for the isolation and characterization of bacteria. Combined disk diffusion methods and PCR were used to screen and confirm ESBL and AmpC production. ESBL was phenotypically detected in E. coli, Klebsiella species, and P. aeruginosa for samples from poultry at the rate of 4%, 1%, and 2% while samples from livestock milieus had ESBL-positive bacteria at the rate of 5%, 2%, 4% for E. coli, Klebsiella species and P. aeruginosa respectively. AmpC was phenotypically detected in E. coli (3%), Klebsiella species (2%), and P. aeruginosa isolates (1%) for samples from poultry milieus. For samples from livestock milieus, AmpC was phenotypically detected in E. coli (7%), Klebsiella species (3%), and P. aeruginosa (6%). The ESBL- and AmpC-positive bacteria showed significant levels of reduced susceptibility to the carbapenems and cephalosporins. PCR detected CTX-M-15 genes (20%) and FOX-1 genes (25%) which mediated ESBL and AmpC resistance in bacteria. These findings have led to the identification of key functional genes that cause bacterial resistance in southeast Nigeria, and focus attention on the importance of surveillance and monitoring to mitigate the transmission of AMR in the environment, as antibiotic therapy could be affected.