Novel genes don’t usually make it into the tourist brochures Jasper James/Getty

Beware the travel bug. In a matter of days after venturing abroad, we acquire genes that make the bacteria living inside us resistant to antibiotics.

Earlier studies had shown that certain genes conferring resistance to antibiotics can be picked up by microbes in your gut when you are abroad. Stool samples from 122 travellers showed that the proportion of antibiotic-resistance genes in their gut bacteria increased from below 10 per cent before they left to as much as 55 per cent on their return.

To find out how quickly these antibiotic-resistance genes could be acquired, the same team took daily stool samples and hand swabs from seven travellers from the Netherlands before, during and after they went to China, India, Canada, South Korea or the Philippines.


The travellers picked up resistance genes as soon as two days after arriving at their destination.

“International travel leads to high acquisition of antibiotic-resistance genes, and we were surprised to see how fast the resistance is acquired,” said Petra Wolffs of Maastricht University Medical Centre in the Netherlands, who presented the results last week at the annual meeting of the American Society for Microbiology in Boston. “Also, we found that the genes can sometimes be retained for a prolonged period after travellers return home,” she said.

Within two days of reaching India, for instance, two travellers had picked up qnrB, a gene that makes bacteria resistant to quinolone, one of the world’s most important antibiotics. The travellers’ gut flora retained the new genes for at least one month after they had returned home.

The type of drug resistance acquired depended on the destination, says Wolffs. In India, for example, widespread resistance to quinolones is well documented, not least because so much of the antibiotic is manufactured and overprescribed there.

One traveller who visited South Korea, as well as another who visited India, picked up CTX-M genes, which make an enzyme called ESBL that can destroy penicillin, cephalosporins and related antibiotics. The percentage of people in South-East Asia who carry these genes has risen from two to 70 per cent over the past decade.

Watch what you eat

Wolffs suspects that food and water containing native bacteria are the most likely source of the new resistance genes. The nature of the study makes it highly unlikely that any of the travellers picked up the genes in flight.

“It may be down to poorer sanitary conditions, providing more opportunities for contamination than in Europe or the USA,” says Willem van Schaik of the University Medical Center Utrecht, the Netherlands, whose own studies track the fate of antibiotic-resistance genes in hospitals and patients. “Wolffs’s results echo many studies showing travel to be a risk factor for infection.”

Reassuringly, none of the travellers in the study suffered any ill effects from the newly acquired genes. “If you’re healthy, it might not have any serious consequences. We’re more worried about people who are immunocompromised and who might be taking antibiotics already – they might be more at risk of some adverse outcome.”

Wolffs is keen to find out whether new resistance genes brought home by a traveller can be passed to friends and family. “That’s work in progress,” she says.