Researchers Find That Antibiotics Should Not Be Taken for Traveler's Diarrhea

The results of a new study show that taking antibiotics for traveler’s diarrhea could increase the risk of acquiring an extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL) infection.

Through overuse and misuse, a number of harmful bacteria have managed to develop resistance to a several currently available antibiotics. Due to the fact that the amount of antibiotic-resistant pathogens continues to increase, it has become a major public health concern. For this reason, healthcare providers across the world are looking into ways to cut down on unnecessary prescriptions and researchers are conducting studies meant to shed additional light on the issue.

One such study took a closer look at millions of travelers who visit high-risk countries each year; countries with notably poor hygiene and “weakly implemented antimicrobial policy.” The researchers, from the University of Helsinki, found that about one third of these aforementioned travelers will come back home with extended-spectrum beta-lactamase-producing Enterobacteriaceae, or ESBL intestinal bacteria. The regions with the highest risk are South Asia, Southeast Asia, Africa, and Latin America. According to study authors, these same regions are “associated with increased risk of travelers’ diarrhea.”

When it comes to traveling to poorer regions of the world, travelers’ diarrhea (TD) “is the most predictable travel-related illness,” according to the Centers for Disease Control and Prevention (CDC), with 30% to 70% of travelers experiencing TD attacks depending on where and when they are traveling. Furthermore, the CDC reports that bacterial pathogens are responsible for a majority of TD cases, namely 80% to 90%. In fact, according to a press release on the Helsinki study, those who contract TD will find themselves at increased risk of acquiring ESBL as well. However, if these individuals choose to treat themselves with antibiotics for TD, their risk of ESBL acquisition “becomes multiplied.” Indeed, a past study conducted by study author Anu Kantele, MD, PhD, professor at the University of Helsinki, found that 80% of individuals who traveled to high-risk areas who contracted TD and took antibiotics as a means to treat their condition, returned carrying ESBL super bacteria.

Dr. Kantele recently spoke with Contagion® about these findings, stating, “In 2015, we published a study in Clinical Infectious Diseases on 430 travelers showing that antibiotic use predisposes the travelers to contract ESBLs. Ninety of our volunteers contracted ESBL during travel. [The properties of ESBL make] the bacterium resistant to two major groups of antibiotics, penicillins and cephalosporins, but they can be sensitive to many other antibiotics as well, such as fluoroquinolones (FQ) and tobramycin. These are the antibiotics we can use for treating ESBL infections, so it is important that the ESBLs are sensitive to these alternative antibiotics.

For this recent study, Dr. Kantele established that taking antibiotics while abroad not only increases the traveler’s risk of acquiring an ESBL infection, but also leads to “the most resistant strains of these bacteria being selected.”

When speaking of the process behind the newest study, Dr. Kantele explained to Contagion®, “We took all the ESBL strains which the 90 persons had contracted and checked what antibiotics they were sensitive to. Then, we divided those persons with the ESBLs into two groups: those who had not taken any antibiotics (but still contracted ESBL, [which] tells about the background risk when you visit such a region) (group FQ-), and those who had taken fluoroquinolone antibiotic (group FQ+). We found that in the FQ- group ([those who] did not take any antibiotics) 37% had an ESBL which was resistant also to FQs. In the FQ+ group, 95% of the ESBLs were resistant to FQ! [This result is] logical as the FQ they have been taking has killed all the sensitive bacteria which would have liked to enter.”

Dr. Kantele went on to stress the importance of these findings, “This whole thing has an important consequence: if a person has taken a certain antibiotic during travel, they get those ESBLs which are resistant to it. So they get ESBLS which are exceptionally broadly resistant to various antibiotics. Such strains are more difficult to treat should you happen to get an infection with it.”

Through the exchange of “packages” that consist of a number of resistance genes, bacteria can transfer resistance to one another, according to the press release; this means that one “package” can possibly possess resistance to a number of different types of antibiotics. The researchers found that most of the ESBL strains that had developed resistance against fluoroquinolones, also exhibited resistance to other types of antibiotics, “the resistance to which is known to be transferred in the same gene packages that transfer ciprofloxacin resistance.”

Dr. Kantele elaborated, “The worst part is that the resistance genes may be transferred in packages and when [you get infected with] a FQ-resistant bug it may be resistant also to tobramycin [and others], so the alternative treatment options are fewer and fewer.”

Though ESBL infections are usually asymptomatic, these bacteria are capable of causing diseases that can potentially result in death. Dr. Kantele stressed that antibiotic resistance poses a significant threat to healthcare in that if antibiotics start to lose their efficacy, a number of infectious diseases can, once again, translate to a death sentence.

Dr. Kantele stressed that the spread of antibiotic-resistant bacterial strains only works to make the problem even worse. When it comes to TD, most cases range only from mild to moderate when it comes to severity, and therefore, antibiotics are not needed for otherwise healthy adults.

“We should take antibiotics during travel only if we are really ill, not for typical travelers’ diarrhea with mild or moderate symptoms. Fever and poor condition are causes for taking antibiotics. Other than that, one should drink adequately, and, if needed, use non-antibiotic antidiarrheal medications,” concluded Dr. Kantele.