Genomic Analysis of Antibiotic Resistance and Virulence Profiles in Escherichia coli Linked to Sternal Bursitis in Chickens: A One Health Perspective

Abstract: Sternal bursitis is an underexplored lesion in poultry, often overlooked in microbiological diagnostics. In this study, we characterized 36 Escherichia coli isolates recovered from sternal bursitis in broiler chickens, combining phenotypic antimicrobial susceptibility testing, PCRbased screening, and whole genome sequencing (WGS). The genetic analysis revealed a diverse population spanning 15 sequence types, including ST155, ST201, and ST58. Resistance to tetracycline and ciprofloxacin was common, and several isolates carried genes encoding β-lactamases, including blaTEM-1B. Chromosomal mutations associated with quinolone and fosfomycin resistance (e.g., gyrA p.S83L, glpT_E448K) were also identified. WGS revealed a high number of virulence-associated genes per isolate (58–96), notably those linked to adhesion (fim, ecp clusters), secretion systems (T6SS), and iron acquisition (ent, fep, fes), suggesting strong pathogenic potential. Many isolates harbored virulence markers typical of ExPEC/APEC, such as iss, ompT, and traT, even in the absence of multidrug resistance. Our findings suggest that E. coli from sternal bursitis may act as reservoirs of resistance and virulence traits relevant to animal and public health. This highlights the need for including such lesions in genomic surveillance programs and reinforces the importance of integrated One Health approaches.

Simple Summary: Sternal bursitis, also known as “breast blisters”, is a relatively neglected inflammatory condition in chickens that can impact animal welfare and food quality. Its bacterial causes are poorly studied. In this work, we investigated the role of Escherichia coli in sternal bursitis by analyzing 36 isolates collected from affected broiler chickens. We examined their resistance to antibiotics, genetic diversity, and the presence of genes that can promote disease. Our results showed that these E. coli strains were genetically diverse, and many carried resistance genes and virulence factors that help bacteria infect animals and survive treatments. Even strains that were not resistant to many antibiotics often possessed many virulence genes. Some of these bacteria also carried traits linked to strains that can cause disease in humans, raising public health concerns. These findings suggest that E. coli associated with sternal bursitis may act as hidden reservoirs of dangerous traits and should be included in surveillance programs. Our study underlines the importance of monitoring such infections as part of an integrated approach to animal and human health.

Keywords

Escherichia Coli Antimicrobial Resistance Broilers Genetic Lineages Poultry Sternal Bursitis One Health Agentes Microbianos e Ambiente Segurança Alimentar Resistência aos Antimicrobianos Infecções Gastrointestinais