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• Posted December 30, 2025

Visiting Abroad In The Coming Year? Antibiotics Becoming Less Effective Against Traveler's Diarrhea, Study Warns

Planning some international travel as one of your New Year’s resolutions?

Then be forewarned: Traveler’s diarrhea is becoming harder to treat.

The antibiotics typically used to treat traveler’s diarrhea are becoming less effective, researchers recently reported in JAMA Network Open.

Specifically, the bacteria that cause the illness are showing increased resistance against two major classes of antibiotics, fluoroquinolones and macrolides, researchers found.

Antibiotic resistance also varies from region to region, depending on the bacteria in question, researchers said.

“These findings suggest that there are wide geographic differences in antibiotic nonsusceptibility patterns in travelers’ diarrhea,” wrote the research team led by Dr. Bhawana Amatya, an infectious disease specialist at CIWEC Hospital and Travel Medicine Center in Kathmandu, Nepal.

For the new study, researchers tested antibiotic effectiveness against the four major strains of bacteria that cause traveler’s diarrhea: Campylobacter, Salmonella, Shigella and E. Coli.

Fluoroquinolone antibiotics include ciprofloxacin, delafloxacin and levofloxacin, according to Drugs.com. Macrolides include azithromycin and erythromycin.

The research team studied 859 cases of traveler’s diarrhea that were treated between April 2015 and December 2022 at 58 tropical medicine centers around the world.

Results showed that:

• 75% of Campylobacter samples were resistant to fluoroquinolones and 12% were resistant to macrolides.

• 32% of Salmonella samples were resistant to fluoroquinolones and 16% were resistant to macrolides.

• 22% of Shigella samples were resistant to fluoroquinolones and 35% were resistant to macrolides.

• 18% of E. Coli samples were resistant to fluoroquinolones.

Overuse of antibiotics is the likely reason why resistance is increasing, said Dr. David Purow, who reviewed the findings. He’s vice president of medicine and GI endoscopy for the Eastern Market at Northwell Health in Huntington, N.Y.

“Bacteria are smart and they can evolve over time,” Purow said in a news release. “That's how resistance develops; multiple different mechanisms view which antimicrobials and bacteria can develop resistance to antibiotics. So, it's basically like anything else: When you start seeing it more and more, you become resistant to it and that's what these bacteria are able to do over time."

Researchers also found that where a person picks up a GI bug can determine which antibiotic will work best.

For example, about 79% of Shigella cases contracted in South Central Asia were resistant to fluoroquinolones, but 78% of Shigella cases in South America were resistant to macrolides.

Both the researchers and Purow said these results indicate that travelers should see a doctor for their diarrhea. Testing can show which antibiotic will work best against the specific bacteria causing their illness.

Currently, many travelers bring antibiotics with them and down the drugs at the first sign of diarrhea, “but we don't actually know what they're treating is susceptible to the antibiotics that they're taking,” Purow said.

Travelers should instead consider taking over-the-counter diarrhea meds, which might help them enough that they don’t need to resort to antibiotics, Purow said.

“Many of these organism bugs will kind of run their course by themselves without necessarily needing treatment,” he said. “However, when people have big trips planned, somebody wants to shorten their symptoms as quickly as they can. So, some of these things can mitigate the symptoms and then people can still enjoy things, but it may not necessarily shorten the duration of symptoms.”

Holding off on antibiotics also can help prevent the further increase of resistance, Purow added.

“It's important that people be aware that just taking antibiotics without knowing specifically what they're treating can have some ramifications for the global population,” he said. “So just being aware and maybe waiting to take antibiotics until the symptoms are a little bit more severe or significant might be helpful here."

More information

The Cleveland Clinic has more on traveler’s diarrhea.

SOURCES: JAMA Network Open, Dec. 22, 2025; Northwell Health, news release, Dec. 22, 2025