Assessment of antimicrobial resistance patterns in bacterial isolates from livestock farms

Thesis Abstract

Rising antimicrobial resistance poses a significant threat to public and animal health, particularly within livestock production systems where extensive use of antibiotics accelerates the emergence and dissemination of resistant bacterial strains. This study aims to assess the prevalence and patterns of antimicrobial resistance among bacterial isolates obtained from livestock farms, with specific objectives to identify prevalent resistant species, determine resistance profiles against commonly used antibiotics, and analyze potential risk factors influencing resistance development. Employing a cross-sectional research design, the study sampled 300 bacterial isolates from 10 livestock farms over a six-month period, encompassing dairy, poultry, and cattle operations. Sampling involved purposive selection of farms based on management practices and antibiotic usage patterns. Data collection integrated microbiological assays for bacterial isolation and identification, which were subsequently subjected to antimicrobial susceptibility testing through the disk diffusion method aligned with Clinical and Laboratory Standards Institute (CLSI) guidelines. The antibiotics tested included tetracycline, ampicillin, sulfamethoxazole-trimethoprim, ciprofloxacin, and chloramphenicol. Data analysis employed descriptive statistics to profile resistance prevalence, while multivariate logistic regression examined associations between farm management practices and resistance patterns. Statistical significance was established at p<0.05, and the results were presented through frequency distributions, resistance pattern matrices, and odds ratios. The study is expected to reveal high levels of resistance to tetracycline and ampicillin among isolates of Escherichia coli and Salmonella spp., with notable multidrug-resistant strains identified in poultry and dairy farms. The resistance patterns are hypothesized to correlate positively with factors such as antibiotic use frequency, farm hygiene standards, and veterinary oversight, consistent with the One Health theoretical framework emphasizing interconnectedness of animal, human, and environmental health. The investigation aims to fill existing gaps in understanding the local dynamics of antimicrobial resistance in livestock settings, which are underrepresented in regional surveillance datasets. It also endeavors to extend existing models of antimicrobial resistance development by integrating socio-economic and operational farm management variables, drawing on the Theory of Planned Behavior for understanding farmer practices. The anticipated findings will contribute to global and regional knowledge on resistance epidemiology, offering insights into specific bacterial species responsible for zoonotic transmission risks and resistance dissemination pathways. Methodologically, the study will demonstrate the importance of integrating microbiological, epidemiological, and behavioral data to formulate targeted intervention strategies. The main contribution lies in providing empirical evidence on resistance patterns that can inform policy frameworks to optimize antibiotic stewardship in veterinary contexts. It also aims to enhance capacity building among veterinary professionals and farmers regarding prudent antibiotic use. The study concludes by recommending the implementation of stringent biosecurity measures, enhanced farmer education programmes, and the development of comprehensive antimicrobial resistance surveillance systems within livestock sectors. Future research should explore molecular mechanisms of resistance and evaluate intervention outcomes to curb resistance escalation in various livestock populations. Overall, this research underscores the urgent need for integrated approaches that address antimicrobial usage and resistance at the farm level to safeguard both animal and human health.