Percorrer por autor "Vieira, Alexandre"
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- The dual action of probiotic lactobacilli in suppressing virulence and survival of Arcobacter butzleriPublication . Vieira, Alexandre; Mateus, Cristiana; Fonseca, Inês M.; Domingues, Fernanda; Oleastro, Mónica; Ferreira, SusanaArcobacter 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 ntagonistic 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.
- The influence of short-chain fatty acids on the survival and virulence of Arcobacter butzleriPublication . Fonseca, Inês M.; Mateus, Cristiana; Vieira, Alexandre; Domingues, Fernanda; Manageiro, Vera; Oleastro, Mónica; Ferreira, SusanaAims: Arcobacter butzleri, a widespread bacterium linked to gastrointestinal disease, can bypass host colonization resistance mechanisms; however, its response to short-chain fatty acids (SCFAs) remains poorly understood. This study investigated the impact of SCFAs on A. butzleri ’s survival and virulence. Methods and results: Eight A. butzleri isolates were assessed under varying concentrations of individual SCFAs and mixtures (m-SCFAs). Higher SCFAs concentrations inhibited bacterial growth in a strain-dependent manner. Transcript analysis of putative virulence genes revealed upregula- tion of ciaB and flaA across most m-SCFAs concentrations, while luxS expression increased at 90 mM. SCFAs generally reduced bacterial motility, with sodium propionate reducing motility but enhancing biofilm-forming ability in the model strain. Additionally, SCFAs exposure decreased the ability of A. butzleri to adhere to and invade the Caco-2 intestinal epithelial cell line. Whole-genome sequencing of the eight A. butzleri isolates revealed extensive genetic diversity, particularly in virulence- and stress-associated genes, although consistent genot ype/phenot ype correlations were not observed. Conclusions: Altogether, these findings demonstrate that SCFAs modulate A. butzleri survival and virulence, providing novel insights into their significance in shaping pathogen behaviour and host-pathogen interactions.