The dual action of probiotic lactobacilli in suppressing virulence and survival of Arcobacter butzleri

Arcobacter butzleri is a widely distributed foodborne and waterborne pathogen, increasingly recognized as an emerging enteropathogen. Understanding its survival mechanisms and interactions with probiotics is crucial for developing targeted intervention strategies. A. butzleri must withstand various hostile conditions to successfully colonize the gastrointestinal tract, including inhibition by probiotics, such as Limosilactobacillus reuteri, Lactobacillus acidophilus and Lactiplantibacillus plantarum. Thus, this study aimed to assess the survival of A. butzleri under acidic conditions and determine its minimum inhibitory concentration (MIC) for bile salts. Additionally, the antimicrobial potential of the lactobacilli strains was evaluated by analysing the effects of their culture-free supernatant (CFS) on A. butzleri growth, coculture interactions, and biofilm formation. The influence of lactobacilli on A. butzleri was further investigated through competition, displacement and exclusion assays using Caco-2 cell models. The results indicate that lactobacilli strains exhibit tolerance to acidic environments and physiological bile salt concentrations, whereas A. butzleri was more susceptible to acidic stress. The antagonistic effect of lactobacilli was evidenced by growth inhibition of A. butzleri in the presence of CFS or during coculture. However, CFS from certain lactobacilli strains was found to enhance biofilm formation, highlighting potential consequences. Furthermore, while lactobacilli did not demonstrate significant antagonistic effects in competition assays, they effectively displaced and excluded A. butzleri in the Caco-2 infection model. Overall, these findings suggest that probiotic lactobacilli can inhibit A. butzleri growth, yet their impact on its virulence remains uncertain. This underscores the need for strain-specific probiotic selection to effectively target this pathogen and emphasizes that not every probiotic contribute to the prevention of A. butzleri infections.