What causes traveller's diarrhoea

Millions of people, every year, have their vacations and business trips ruined when they get ‘traveller’s diarrhoea’ during travelling.

A major cause of this is a bacteria called Enterotoxigenic E. coli, or ETEC. Researchers have discovered how the bacteria work to cause the conditionin an effort to develop a preventive vaccine for travellers.

The researchers studied samples taken directly from citizens who volunteered to become infected with ETEC.

Ingesting contaminated food or water can lead to ETEC infection, which can cause diarrhoea for up to a week. Considering the fact that up to 200 million people become infected annually, an estimated 1 billion days of human productivity are lost every year due to ETEC infections.

Visiting the doctor to get vaccinated before a trip can prevent travellers from catching a disease. Unfortunately, there are no available vaccines to prevent ETEC infections, so travellers must constantly be concerned about what they eat and drink while on vacation.

The group examined how ETEC behaved inside humans during infection compared to how it behaved in the laboratory. They were surprised to find that ETEC produced more toxins when grown in the laboratory than it did in human infection samples.

They discovered that ETEC could sense oxygen in the atmosphere, and that controlled the amount of toxins produced by ETEC. This explained their surprising data: There is more oxygen in the atmosphere than there is in the digestive tract, which resulted in the differing levels of toxin expression.

This breakthrough gives researchers hope that they have identified the “cue” that ETEC uses to determine when to make toxins that cause disease. How ETEC causes disease via toxins has been studied exhaustively for decades. Previous groups have identified numerous factors that contribute to toxin production in ETEC, but this is the first-time oxygen has been identified as a major player in ETEC virulence.

Lead author Alex Crofts said, “We think ETEC can sense the oxygen given off by our own cells as a cue to produce toxins.”

The group now hopes to use this oxygen-sensitive ETEC response against the bacteria to prevent infections.

“Beyond toxins, we found ETEC regulates many other factors in response to oxygen, and some of those are promising new targets for future vaccines. ETEC is a global burden on society, and we are doing all we can to advance our understanding of the disease,” said study author Stephen Trent.

The study appeared in the journal ‘Proceedings of the National Academy of Sciences’.