Campylobacter uses Trojan horse infiltration technique

The Greeks did it to Troy — leaving a giant wooden horse at the city gates and pretending to sail away. The Trojans took the horse into the city, assuming it was a peace offering, only to find they had inadvertently let Greek soldiers into their city. And the rest is history.

Now it seems that Campylobacter jejuni is employing a similar technique when it invades our bodies and causes gastroenteritis. The usual culprit for giving us a bout of Campylobacter jejuni-induced food poisoning is raw or undercooked chicken, but how do enough bacteria survive our digestive systems to cause sickness?

They infiltrate amoebae and, while protected from the harsh digestive conditions, the Campylobacter jejuni multiply so when they break out they are there in high numbers. The Trojan horse story revisited.

Kingston University researchers, including PhD student Ana Vieira, explored the relationship between the bacteria and amoebae to better understand how bacteria survive and how to prevent the spread of infection.

Campylobacter and its amoebic hosts often exist in the same environments — such as in drinking water for chickens on poultry farms — which could increase the risk of infection, according to Vieira. “The amoeba may act as a protective host against some disinfection procedures, so the findings could be used to explore new ways of helping prevent the bacteria’s spread by breaking the chain of infection.”

The relationship between Campylobacter and amoebae has been hotly debated in scientific circles — with conflicting findings in previous studies as to whether the bacteria multiply inside, or only in the beneficial environment around, amoebae cells.

The Kingston University team used a modification of a process that assesses the bacteria’s ability to invade cells — called the gentamycin protection assay — to confirm they can survive and multiply while inside the amoeba’s protective environment.

This allows Campylobacter to thrive, escaping the amoeba cells in larger numbers — shining a light on how it spreads and causes disease, according to Professor Andrey Karlyshev, a supervisor on the study.

“Our research gives us a better understanding of bacterial survival,” he said. “Because amoebae are widespread, we have shown how Campylobacter bacteria are able to use them as a Trojan horse for infection of the food chain. Otherwise they wouldn’t survive, as they are very sensitive to the environment.”

Professor Andrey Karlyshev said Campylobacter’s ability to multiply inside ameobae cells helps protect it from harsh environmental conditions. As part of the study, the researchers showed how a system used by the bacteria to expel toxins — known as a multidrug efflux pump — plays a key role in its ability to thrive within the amoebae.

The team examined how this system helps the bacteria become resistant to antibiotics, which could lead to new methods of preventing resistance from developing, Professor Karlyshev added.

“Campylobacter is becoming increasingly resistant to antibiotics because of their wide use on humans and animals,” he said. “Due to its role in antibiotic resistance and bacterial survival in amoebae, the efflux pump could prove to be a good target for the development of antibacterial drugs.

“Targeting the bacterial factors required for survival within amoebae could help to prevent Campylobacter from spreading in the environment and colonising chickens. This is turn could help reduce its ability to enter the food chain and cause disease in humans.”

    

PhD student Ana Vieira and Professor Andrey Karlyshev.