NEW YORK (Reuters Health) – Acquisition and spread of drug-resistant infections among international travelers is “substantial and worrisome,” researchers say.

“Previous studies had already indicated that a significant (proportion) of long-distance travelers acquire multidrug resistant bacteria (in particular extended-spectrum beta-lactamase and carbapenemase-producing Enterobacteriaceae or ESBL-E) during travel,” Dr. John Penders of the University of Maastrich, The Netherlands, told Reuters Health.

“Our aim was to gain more insight into the acquisition of multidrug resistant bacteria per travel destination, to identify potential risk factors for acquisition and to estimate the duration of colonization upon acquisition,” he said by email. “Moreover, we wanted to estimate the potential onward transmission of these multidrug resistant bacteria from the travelers to their household members once they returned.”

As reported in The Lancet Infectious Diseases, online October 14, Dr. Penders and colleagues recruited 2001 Dutch travelers and 215 household members who did not travel. They collected fecal samples and asked participants to complete questionnaires before travel, immediately upon return, and one, three, six, and 12 months after their return.

All fecal samples were screened for the presence of ESBL-E. Post-travel samples underwent additional testing for specific plasmid-encoded beta lactamase enzymes to confirm the presence of ESBL.

Dr. Penders said, “We found that over 34% of all travelers who were negative for ESBL-E before travel acquired ESBL-E during international travel. However, the acquisition rates varied widely according to travel destination, with ESBL-E acquisition in 75% of travelers to southern Asia and 40-50% of those to central and eastern Asia, western Asia and northern Africa.”

“Next to travel destination, important risk factors for ESBL-E acquisition were antibiotic use during travel (adjusted odds ratio, 2.69), traveler’s diarrhea (AOR 2.31) and pre-existing chronic bowel disease (AOR, 2.10),” he continued. “The median duration of colonization after travel was 30 days, but 11% of the travelers remained colonized for at least 12 months after travel.”

“Moreover, we found that the probability of transmitting ESBL-E to another household member was 12%,” he said. By comparison, a 23% transmission rate from recently discharged patients to their caregiving household members has been reported, his team notes.

“The high frequencies of ESBL-E acquisition during travel, the subsequent sustained carriage and the evidence of onward transmission within households show that travelers substantially contribute to the emergence and spread of ESBL-E on a global scale,” Dr. Penders said.

“Active screening for multidrug resistant Enterobacteriaceae and adjustment of empirical antimicrobial therapy should be considered for returning travelers at increased risk of ESBL-E carriage,” he added.

He continued, “However, it is important to note that the implications for infection prevention and antibiotic treatment policies will differ locally because the impact of acquisition and spread of ESBL-E by travelers is highly dependent on the local ESBL-E prevalence in the country of origin.”

Dr. Antoine Andremont of Bichat-Claude Bernard University Hospital in Paris, France, coauthor of an accompanying editorial, told Reuters Health, “Resistance of bacteria to antibiotics has reached alarming levels in hospitalized patients but so far has had relatively low impact on GP practice in the community.”

“This is, however, rapidly changing with the evidence that travelers to tropical areas very often come back home carrying multiresistant bacteria in their intestine for a few months. This is not a disease per se, but carriers are more prone to develop multiresistant infections, for instance, urinary tract infections, that may not be treated as easily as usual,” he explained by email.

Dr. Andremont concluded, “Therefore, GPs must now be aware of this risk and be prepared to adapt their practice in case of first-line treatment failure. Bacterial resistance is indeed a major holistic problem that will be solved only if we collectively manage to reduce all abuse and misuse of antibiotics in humans well as in animal medicine and in food chain production.”

Dr. Andremont has received personal fees from biotech company DaVolterra, which develops antibiotics.