Dissecting the Antibacterial Role of Campylobacter's Type VI Secretion System and Effectors Across Diverse Host Environments

Campylobacter is the leading cause of foodborne diseases annually in the UK, costing the country's economy a significant amount of money each year. Specifically, the Food Standards Agency estimates that Campylobacter infections alone incur a hefty £900 million expense, out of a total of £1.5 billion for all foodborne infections. Particularly, Campylobacter jejuni species is responsible for over 80% of these cases. This bacterium is becoming increasingly resistant to commonly used antibiotics. Remarkably, it naturally resides in birds, where trillions of these bacteria coexist in their guts without causing harm. However, just 100 of these bacteria can lead to severe illness in humans. Consuming or handling poultry is the main way humans contract the infection, which can result in symptoms like bloody diarrhoea, fever, and abdominal pain. In areas with limited resources, Campylobacter infections are particularly prevalent among young children, leading to health issues such as stunted growth, lifelong physical and cognitive impairments, and in severe cases, death.
Despite its prevalence and importance, our understanding of how C. jejuni causes disease is limited when compared to other gut pathogens such as Salmonella. Recently, we have identified many strains of C. jejuni that have a Type VI Secretion System (T6SS). The T6SS acts as a weapon firing bullets (toxins known as effector proteins) that neutralise bacterial competitors, thereby conferring them a competitive edge within a host environment. The functions of C. jejuni T6SS effectors, particularly in chicken and human host environments and their impact on the resulting infection outcome remains unclear.
Our research suggests that T6SS and its effectors equip C. jejuni with antibacterial properties to thrive in specific host environments. By analysing the genomes of C. jejuni, we have identified a new range of these effectors and we hypothesise that these are important mediators of C. jejuni...