Blue light could cut food poisoning from raw chicken

A low-power blue light could be the key to significantly reducing food poisoning caused by raw chicken in the UK, scientists at the University of Reading have found.

Campylobacter is the most common cause of bacterial food poisoning worldwide. In the UK alone there are hundreds of thousands of cases each year, costing an estimated £700 million annually in healthcare and lost productivity.

In a study published today [6 October] in the journal Microbiology, researchers from Reading, working in collaboration with the Animal and Plant Health Agency, tested a new technique known as violet-blue photodynamic inactivation (VB-PDI) against 64 different strains of Campylobacter, which is found in around three quarters of all raw chicken sold in the UK. Every single strain was killed by the treatment, regardless of species or antibiotic resistance profile.

The findings build on previous research that showed blue light treatments could work more effectively than treating chicken with chlorine to kill off specific strains of bacteria. Chlorinated chicken is common in the US, but is not commonly found in Europe, and is a high-profile example of differing food standards and trade barriers between US and Europe.

While cooking kills Campylobacter, cross-contamination from handling raw meat is thought to be the main route of infection. Symptoms typically last about a week and include stomach cramps, fever, nausea and, in many cases, bloody diarrhoea.

VB-PDI works by shining a safe, visible violet-blue light onto bacteria, causing molecules naturally found inside their cells to produce lethal levels of destructive compounds called reactive oxygen species. Crucially, the method needs no physical contact with the food and no added chemicals, making it a promising option for use on poultry carcasses in processing plants after slaughter, before products reach consumers.

The researchers estimate that if the technique could reduce contamination on chicken carcasses by a factor of 100, the proportion of highly contaminated carcasses reaching retail could fall from around 1 in 10 to just 1 in 50.

The team also found no evidence that Campylobacter bacteria could develop resistance to the treatment. Strains that were already resistant to antibiotics were killed just as effectively as fully susceptible ones. When one strain was repeatedly exposed to the light over 15 rounds in the laboratory, in an attempt to force resistance to evolve, no increase in tolerance was seen.

Dr Aidan Taylor, from the University of Reading and lead author of the study, said: "Campylobacter is a genuinely nasty bug, and its sheer abundance in the food chain, combined with rising antibiotic resistance, makes it a really difficult problem to tackle.

“What's exciting about this light-based approach is that it doesn't rely on chemicals or antibiotics at all, so it sidesteps the resistance problem entirely. We've shown it works against a wide range of real-world strains taken directly from UK poultry, including the multi-drug resistant strains that worry us most, and we can't find any evidence that resistance could evolve. That combination of broad efficacy and durability is what makes this such a promising option for cutting contamination before chicken ever reaches someone's kitchen."

Because VB-PDI uses simple, low-power LEDs with a long lifespan and minimal running costs, the team also believe it could offer a low-cost option for poultry producers, including in low- and middle-income countries where food safety infrastructure is limited.

The Animal and Plant Health Agency surveillance programme provides a uniquely detailed picture of the Campylobacter strains circulating in UK poultry. This allowed scientists to test the technology against a real diversity of bacteria, rather than laboratory strains alone.

Dr Samuel Connelly, from the Animal and Plant Health Agency, who co-led the research, said: “The consistent results observed across multiple species and resistance profiles are highly encouraging. While further evaluation using contaminated meat samples is required, the simplicity and adaptability of this technology suggest that it could be implemented at various stages of the food production process. Such application has the potential to reduce the prevalence of Campylobacter within the food chain and, consequently, contribute to a reduction in the incidence of foodborne illness.”

Earlier work by the same team uncovered the molecular reasons why Campylobacter is so sensitive to violet-blue light. The researchers say further trials on naturally contaminated poultry carcasses in real processing settings are now needed before the technology could be rolled out commercially.

Full reference: Finlay Bembridge, Jack K. Whitmore, Adrian M. Ciesielski, John D. Rodgers, Samuel A. M. Connelly and Aidan J. Taylor, One light to rule them all: photodynamic inactivation of diverse Campylobacter, Microbiology. https://doi.org/10.1099/mic.0.001769