Simple blue light could make raw chicken safer, even from drug-resistant bacteria

A low-power violet-blue LED cut 64 strains of Campylobacter, a common food poisoning germ on raw chicken, by at least 99% in lab tests.

Bacteria have a habit of outlasting whatever people use against them, and that's how antibiotic resistance became a worldwide problem. A beam of violet-blue light may be much harder to outlast.

In laboratory tests, light from a single low-power LED cut every one of 64 strains of a common food poisoning bacterium by at least 99%. That included strains that resist several antibiotics. And when one strain was exposed to the light 15 times over, it got no harder to kill.

That makes the light a promising way to cut contamination on raw chicken before it ever reaches a store.

Finlay Bembridge and colleagues in Aidan Taylor's lab at the University of Reading in England ran the tests. They worked with Samuel Connelly's team at the UK's Animal and Plant Health Agency (APHA). So far, the bacteria have been tested floating in liquid in the lab, not on chicken skin.

Why raw chicken is risky

The bacterium is Campylobacter, the most common cause of bacterial food poisoning worldwide. Its most common species reaches people mainly through poultry.

The UK recorded about 70,000 lab-confirmed cases in 2024 and 2025, the highest numbers on record. Because many cases go unreported, the true number is thought to be about ten times higher. The cost in healthcare and lost work is estimated at about £700 million a year.

Roughly two-thirds of raw chicken sold in UK shops is contaminated. Most infections bring about a week of stomach illness, often with bloody diarrhea, and up to one case in 10 is serious enough for a hospital stay.

In an interview with Earth.com, Taylor said the risk comes from handling the raw meat. "Cooking chicken thoroughly will kill all the bacteria, so there is no risk once cooked," he said.

He said cooks shouldn't reuse utensils or cutting boards once they've touched raw chicken, and should wash their hands right after. "Chicken should never be washed, as this will spread the bacteria everywhere around the sink area," Taylor said. The key, he added, is avoiding cross-contamination in the kitchen.

How the light kills bacteria

The light has a wavelength of 405 nanometers, which puts it at the violet edge of what human eyes can see, just short of ultraviolet. Certain molecules inside Campylobacter absorb that light and turn it into damaging forms of oxygen.

The bacterium carries unusually large amounts of one of them, a molecule the cell uses to build heme. It also depends on enzymes it can't live without, and oxygen damages them easily.

Taylor's team worked out that weakness in a 2022 study of standard lab strains. What they still needed to know was whether the light would work just as well on the many different strains found on real farms.

A genetic search suggested it would. Across 6,658 Campylobacter genomes from 53 species, the genes behind that sensitivity turned up every time.

All 64 strains were vulnerable

The 64 strains came from national surveillance of UK poultry between 2008 and 2024, sampled from chicken guts, broiler farms and turkeys. Each was grown from its own sample, which scientists call an isolate.

They covered three species: 43 of C. jejuni, 14 of C. coli and seven of C. lari.

The team shone the light on each strain at three doses. Every strain lost more bacteria as the dose rose. At the highest dose, each one fell by at least 99%, and 44% of them fell by more than 99.99%.

No species did better than the others. On average, the farm strains were easier to kill than the standard lab strain from the team's earlier work.

Given enough time, the light left no bacteria the team could detect. In a timed test on several strains, no living bacteria could be found after 15 minutes at the stronger setting. The team also found no persister cells, the small groups of dormant bacteria that sometimes survive even huge doses of antibiotics.

Some Campylobacter strains can survive for long stretches in open air, and those are thought to last longer on chicken carcasses. They died just as readily as the rest.

Drug resistance made no difference

Many of the strains could already withstand common antibiotics. Forty of the 64 were resistant to ciprofloxacin, and 36 to tetracycline. Eleven resisted ertapenem, a type of resistance that has been spreading in UK poultry since monitoring for it began in 2022.

None of that changed how the light worked. Resistant strains and fully susceptible ones lost bacteria at the same rate, and so did those that resisted three or more classes of drugs. Bacteria grown with low doses of ciprofloxacin, which might have primed their defenses, were no harder to kill.

That matters because antibiotic resistance in these bacteria keeps rising in UK poultry. It's rising even though antibiotic sales for broiler chickens have fallen by 77% since 2014.

"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," Taylor said.

The bacteria failed to adapt

Some antibiotics can stop working after a single lucky mutation. In Campylobacter, one change in one gene is enough to beat ciprofloxacin.

The light works differently. It damages many parts of the cell at once, and the researchers couldn't imagine a plausible set of mutations that would give strong protection against all of it.

To test that, the team took one farm strain of average sensitivity and split it into three separate lines. Each line went under the light 15 times.

Every round killed about 99.9% of the bacteria, and the survivors were regrown and exposed again. After all 15 rounds, none of the three lines was any harder to kill than the strain they started from.

Asked by Earth.com what surprised him most, Taylor said the team's earlier work had predicted this result. To resist the light, the bacteria would have to give up parts of their own machinery they can't survive without.

"The surprising part was that this hypothesis appears to actually be correct!" he said. "Bacteria are remarkably adaptable and in reality we expected to find some isolates which had evolved a workaround we couldn't foresee."

The researchers still call the risk of resistance minimal rather than zero. Only one strain went through the repeat test, and they wrote that more work is needed to rule resistance out.

From the lab to the plant

Because the light needs no chemicals and no contact with food, the team pictures it treating carcasses at processing plants after slaughter. The LEDs use little power and last a long time, which the researchers said could suit producers in poorer countries too.

A whole chicken counts as highly contaminated above about 1,000 bacteria per gram of skin, and a 2023 survey found 10% of supermarket chickens over that line. A 100-fold cut would bring that share down to 2%, below the Food Standards Agency target of 7%.

Putting that into practice is another matter. Some processing plants handle more than 10,000 birds an hour.

"One challenge is the speed at which poultry move through processing plants, meaning we have a very short window of opportunity to apply the treatment," Taylor told Earth.com.

Bacteria stuck to chicken skin, or packed into slimy films on plant surfaces, may also be shielded from the light. "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," said Connelly, who co-led the research.

The light hasn't yet been tried on naturally contaminated chicken in a working plant, so it's unknown how much of that 99% would hold up on a moving carcass. Taylor hopes plant trials can begin in the near future, but said it's too early to guess when the light might reach a production line.

The full study was published in the journal Microbiology.

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