Travellers to developing countries who take antibiotics to prevent diarrhoea, or the infamous 'Delhi belly' may be putting themselves at higher risk of contracting super-bugs and spreading these drug-resistant bacteria in their home countries, according to a new study.
The study's authors call for greater caution in using antibiotics for travellers' diarrhoea, except in severe cases, as part of broader efforts to fight the growing public health crisis of antibiotic resistance and the spread of highly resistant bacteria worldwide.
"The great majority of all cases of travellers' diarrhoea are mild and resolve on their own," said lead study author Anu Kantele, associate professor in infectious diseases at Helsinki University Hospital in Finland.
Researchers collected stool samples for testing from 430 Finns before and after they travelled outside of Scandinavia.
Their goal was to determine if their guts became colonised by a resistant type of bacteria from the Enterobacteriaceae family that produces a key enzyme, extended-spectrum beta-lactamase (ESBL), which confers resistance to many commonly used antibiotics.
The researchers looked for risk factors in the travellers' behaviour that may have facilitated colonisation by these resistant bacteria.
The US Centre for Disease Control and Prevention has called ESBL-producing bacteria a serious concern and a significant threat to public health.
The bacteria can cause severe infections that are harder and more expensive to treat and more likely to be fatal.
The Finnish travellers completed surveys about their trips, including questions about diarrhoea and antibiotic use, which can disrupt the gut's balanced ecosystem, sometimes allowing resistant bacteria to become incorporated into the intestinal ecosystem.
Overall, 21 per cent of the travellers to tropical and subtropical areas in the study had unknowingly contracted ESBL-producing bacteria during their trips.
Significant risk factors for colonisation were travellers' diarrhoea and treating it with antibiotics while abroad. Among those who took antibiotics for diarrhoea, 37 per cent were colonised, researchers said.
Those travelling to South Asia (including India) faced the highest risk of contracting the resistant bacteria: 80 per cent of travellers who took antibiotics for diarrhoea while visiting the region were colonised with ESBL bacteria.
Southeast Asia, East Asia, and North Africa together with the Middle East, in order, were next highest in risk.
Even if colonised travellers do not develop infections themselves, they may, after returning home, unknowingly spread the superbugs to their own developed countries, where today these bacteria are less prevalent, researchers said.
The study was published in Clinical Infectious Diseases.