Taking antibiotics for diarrhoea may put travellers visiting developing parts of the world at higher risk for contracting superbugs and spreading these daunting drug-resistant bacteria to their home countries, according to a new study. Science Codex reports that the study 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 Dr Anu Kantele, associate professor in infectious diseases at Helsinki University Hospital, Finland.
In the study, researchers collected stool samples for testing from 430 Finns before and after they travelled outside of Scandinavia. The goal: 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 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% 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% were colonised. Those travelling to South Asia faced the highest risk of contracting the resistant bacteria: 80% 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. A laboratory survey showed that none of the 90 colonised travellers in the study developed infections caused by the resistant bacteria during the next year. Had the number of colonised travellers been slightly larger, Kantele noted, symptomatic infections would probably have been detected.
"More than 300 million people visit these high-risk regions every year," Kantele said. "If approximately 20% of them are colonised with the bugs, these are really huge numbers. This is a serious thing. The only positive thing is that the colonisation is usually transient, lasting for around half a year."
Greater attention should be aimed at educating international travellers to take a more cautious attitude toward antibiotics, the study authors wrote. In general, Kantele said, travellers with diarrhoea should drink plenty of fluids to avoid dehydration, use non-antibiotic antidiarrhoeal drugs available over the counter to help relieve symptoms if needed, and seek medical attention for severe cases, such as those with high fever, bloody stools, or serious dehydration.
In a related editorial, Dr Bradley A Connor of Weill Cornell Medical College and Dr Jay S Keystone of Toronto General Hospital noted that the study provides compelling evidence that antibiotic use increases travellers' risk of colonisation by ESBL-producing bacteria. They note additional research is needed on what criteria should guide travellers' use of antibiotics for severe diarrhoea, the effect of travel on the gut microbiome, and new preventive measures travellers can use to avoid diarrhoea.
[link url="http://www.sciencecodex.com/antibiotic_use_by_travelers_may_add_to_global_spread_of_superbugs-149324"]Full Science Codex report[/link]
[link url="http://www.oxfordjournals.org/our_journals/cid/prpaper.pdf"]Clinical Infectious Diseases abstract[/link]
[link url="http://www.oxfordjournals.org/our_journals/cid/preditorial.pdf"]Clinical Infectious Diseases editorial[/link]