Bacteria-hunters ‘walk the talk’

ONCE every three weeks for 16 months, and more frequently in the springtime, a group of 60 volunteers put a sock on the outside of one shoe and went for 4km walks through the British outdoors.

Then, wearing gloves, the walkers peeled the socks off their feet, placed them in biohazard bags and mailed them to laboratories run by Public Health England and the University of Liverpool.

These socks, and soil stuck to them, were crucial components in the first outdoor survey of its kind – an attempt to gauge the wild population of campylobacter microbes using the feet of citizen scientists.

Campylobacter can cause foodborne disease, often from contaminated poultry or beef, and recent studies show signs of the germs’ increasing resistance to antibiotics. Campylobacter infections are among the most common causes of diarrhoea, responsible for an estimated 1.3 million gastrointestinal illnesses in the US annually.

“It is known that food is often a source of campylobacter infections in humans, but we also know that exposure through food cannot explain all the cases seen in the human population,” Natalia Jones, co-author of the study, said.

The report demonstrated that the bugs are indeed present in the wild. Of 720 socks assessed, 47% tested positive for the bacteria.

More socks tested positive for the bacteria when it was cold and wet. It was possible that the germs thrived in the rainfall, the study authors wrote, but that could also reflect better adherence of bacteria to damp socks.

“This research could lead to interventions to reduce the risk to humans,” Jones said.