Campylobacteriosis is the predominant zoonotic infection in Europe and poses a significant public health concern due to its potential to cause severe sequelae, including peripheral neuropathies, Guillain–Barré syndrome, Miller-Fisher syndrome, and functional bowel disorders such as irritable bowel syndrome. The primary causative agents, Campylobacter coli and Campylobacter jejuni, inhabit domestic animals like poultry, cattle, and pigs, along with wild birds, acting as commensals. Poultry meat is identified as the major source of infection and, when transmitted to humans through ingestion, these bacteria follow a pathogenic route. Despite various strategies at both management and treatment levels to reduce Campylobacter in poultry, the effectiveness of many probiotics as feed additives, particularly Bacillus subtilis PS-216, requires comprehensive investigation.

The aim of this study was to investigate at the proteome level the in vitro interaction between C. jejuni and B. subtilis, with a specific focus on comparing C. jejuni strains possessing the virulence factor Type 6 Secretion System (T6SS) and strains not possessing it. T6SS is a relevant element to consider since it can function as a potent weapon against host cells and other bacteria, adding a layer of complexity to Campylobacter pathogenicity.

In this study, a proteogenomics approach was used to evaluate in parallel the growth dynamics in coculture and the production of antimicrobial and signalling proteins by B. subtilis in response to the T6SS presence or absence. We initially monitored the growth differences of C. jejuni strains through bacterial monoculture and coculture with B. subtilis in Mueller Hilton Broth in microaerobic conditions. In parallel, the study assessed the functional proteome remodelling of B. subtilis during the interaction with C. jejuni with and without T6SS. In summary, this investigation aimed to advance our understanding of Campylobacteriosis by exploring the dynamics of C. jejuni and B. subtilis interaction, shedding light on potential avenues for targeted interventions and preventive measures.