‘Travelers diarrhea’ is a common experience, particularly among people visiting developing parts of the world. The ailment is often treated with antibiotics, but new research suggests that this practice could put travelers at higher risk of contracting superbugs and spreading these daunting drug-resistant bacteria to their home countries.
According to the Centers for Disease Control and Prevention (CDC), travelers’ diarrhea is the most common illness to affect travelers. An estimated 10 million people — 20 to 50 percent of international travelers — develop the condition, usually occurring within the first week of travel.
In most instances, the use of antibiotics is unnecessary. “The great majority of all cases of travelers’ diarrhea are mild and resolve on their own,” says lead author Dr. Anu Kantele, MD, PhD, associate professor in infectious diseases at Helsinki University Hospital in Finland.
The authors report that every year, around 300 million travelers visit regions where antimicrobial resistance is a growing risk. Of these travelers, more than 20 percent return to their home countries colonized by resistant intestinal bacteria.
Dr. Kantele’s team focused on bacteria from the Enterobacteriaceae family, which can produce a particular enzyme in the gut called extended-spectrum beta-lactamase (ESBL). This enzyme is known to promote resistance to several frequently-used antibiotics.
Measuring colonization from ESBL-producing bacteria
The CDC 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.
For the study, published in the journal Clinical Infectious Diseases, the authors analyzed stool samples from 430 Finns before and after traveling outside of Scandinavia for more than four nights to see how many contracted ESBL-producing bacteria while on their travels.
Participants were also asked to complete two questionnaires. The first, a pre-travel survey regarding personal information, medical history and a travel itinerary. Upon returning, the travelers filled out the second questionnaire, concerning their trip and including questions about possible symptoms and medication taken.
The researchers found that 21 percent of the participants contracted ESBL-producing bacteria while traveling. Risk factors identified for colonization were the region the participants traveled to, age, occurrence of travelers’ diarrhea and use of antibiotics for the treatment of diarrhea.
Among participants taking antibiotics to treat their diarrhea, 37 percent became colonized. Among travelers visiting the riskiest region for resistant bacteria contraction — South Asia — a whopping 80 percent of those taking antibiotics for diarrhea contracted ESBL-producing bacteria.
Colonization with resistant bacteria ‘is a serious thing’
None of the 90 travelers that were colonized by the bacteria went on to develop infections as a result, though the risk of the bacteria spreading from the travelers was still present. Dr. Kantele believes that a larger sample of colonized travelers would probably have yielded infection cases.
“More than 300 million people visit these high-risk regions every year,” she said. “If approximately 20 percent of them are colonized with the bugs, these are really huge numbers. This is a serious thing. The only positive thing is that the colonization is usually transient, lasting for around half a year.”
Furthermore, said Dr. Kantele, travelers who return home with ESBL-producing bacteria in their gut may unknowingly spread these superbugs to their own home countries, even if they do not develop infections themselves.
Although the study was the largest on this subject to date, the sample size was still small for travelers visiting a number of regions, including East Asia, North Africa and the Middle East. Data acquired from the study were also observational and, therefore, further research will be needed to determine causation.
For now, the authors say the best way to avoid colonization from ESBL-producing bacteria is by preventing travelers’ diarrhea and restricting the use of antibiotics to treat the condition. “If travelers were instructed to be more cautious in their use of antimicrobials, the number of colonized individuals could decrease dramatically,” they conclude.
The authors of a related editorial, also published in Clinical Infectious Diseases, suggest that future studies should investigate the effect of travel on the gut microbiome, measures to prevent travelers’ diarrhea, and what criteria should inform the use of antibiotics for severe cases.
According to a review published last month, drug-resistant superbugs could kill 10 million people a year by 2050, resulting in a reduction of 2 percent to 3.5 percent in gross domestic product worldwide and exacting a global price of about $100 trillion annually.