Resistance patterns and gene expression profiles of Arcobacter butzleri under exposure to selected antibiotics and disinfectants.

The rapid emergence and spread of antimicrobial resistance (AMR) pose a major global threat to public health. Beyond antibiotics, disinfectants used in food-processing environments may also exert selective pressure that promotes bacterial responses overlapping with antibiotic resistance mechanisms. This study explored the interconnection between antibiotic and disinfectant resistance of the pathogen Arcobacter butzleri by combining phenotypic and transcriptomic analyses. Thirty-one strains isolated from a poultry slaughterhouse were screened for susceptibility to antibiotics from different classes and to commonly used disinfectants. Following an initial screening, 3 representative strains were selected for in-depth analyses and exposed to erythromycin and amoxicillin - clavulanic acid, an amine-based and a sodium hypochlorite with caustic potash disinfectants. Bacterial load, metabolic activity, and transcriptomic responses, using RNA sequencing (RNA-seq), were assesed. All strains exhibited high levels of antibiotic resistance, including resistance to tetracycline and ampicillin. Antibiotic exposure was characterised by minimal reductions in bacterial load and few differentially expressed genes. In contrast, disinfectant exposure induced pronounced, strain-specific responses and resulted in the activation of multiple adaptive pathways. Differential gene expression involved chemotaxis regulators, DNA recombination, detoxification processes, Gram-negative cell wall components, protein and RNA processing systems. Notably, several genes associated with virulence and AMR (tonB, hecB, mexA, mexB, mviN, phoP, tetR, and ylaC), were overexpressed following disinfectants exposure, suggesting potential selection of virulence determinants following disinfectants exposure. The ability of A. butzleri to activate strain-specific adaptive mechanisms in response to antibiotics and disinfectants exposure may facilitate its persistence in food-processing environments and contribute to its pathogenic potential.