Escherichia coli presence in someone’s gut increases their likelihood of developing a urinary tract infection (UTI), particularly with certain E. coli strains.
This remains true for at least 18 months after E. coli has been detected, according to new research. In addition, the study found a sizable portion of gut E. coli was resistant to one or more commonly used antibiotics.
“We knew that UTIs are caused by bacteria coming from the gut. But it was surprising that having certain gut-colonizing E. coli increased the likelihood of getting a UTI for up to 18 months,” said study senior author Evgeni V. Sokurenko, MD, PhD, a microbiologist at the University of Washington School of Medicine, in Seattle.
In collaboration with Kaiser Permanente Washington, researchers collected and examined E. coli strains in fecal samples from 1,804 women 50 years of age and older who had not received an antibiotic prescription for at least a year before the study began.
More than 90% of the fecal samples had E. coli. Fully 24% of these samples contained strains resistant to trimethoprim-sulfamethoxazole; 19% harbored strains resistant to ciprofloxacin; and 8% had strains resistant to third-generation cephalosporins.
Eighteen months after providing fecal samples, 10.2% of people colonized with E. coli developed a UTI, compared with only 3% in those without it (P=0.0013). UTI risk among carriers of a pandemic multidrug-resistant strain—E. coli ST131-H30—was especially high (24.3%; P=0.0004). UTI probability increased with age; 14.2% of women 70 years and older developed a UTI (P<0.001), a proportion that rose to 37.8% with E. coli H30 (P<0.001).
Dr. Sokurenko stressed that none of the women had taken an antibiotic for more than a year before the UTI, yet still often ended up with antibiotic-resistant infection.
“Cutting antibiotics use may not considerably reduce the rise of resistant UTI pathogens. We need to develop other means to curb the problem faster,” Dr. Sokurenko said.
Treating UTIs
Increasing antimicrobial resistance has made treating UTIs more challenging, noted Lori Burrows, PhD, FAAM, FCAHS, a professor of biochemistry and an infectious disease researcher at McMaster University, in Hamilton, Ontario.
“UTIs used to be easy to treat. Now they’re not so easy, leading to more time off work. It’s a big burden on the medical system and on people’s time,” Dr. Burrows said, specifically women, who are more likely to acquire a UTI.
Current options for treatment are expanding, albeit slowly, according to Dr. Burrows. “There’s not a lot of new treatments coming down the pike,” Dr. Burrows said.
However, in 2024, the FDA approved the use of pivmecillinam (Pivya, Utility Therapeutics) for uncomplicated UTIs without signs of resistance, as well as sulopenem etzadroxil (Orlynvah, Iterum Therapeutics) for uncomplicated UTIs caused by specific bacteria in adult women with limited or no alternative oral antibacterial treatment options. For complicated UTIs, the FDA approved cefepime-enmetazobactam (Exblifep, Allecra). This year, the FDA approved the first drug in a new class of antibiotic for UTIs in almost 30 years, gepotidacin (Blujepa, GlaxoSmithKline), for the treatment of uncomplicated UTIs caused by susceptible organisms in adult women and girls 12 years of age and older.
Moving Beyond Antibiotics
Clinicians and public health educators can encourage good hygiene to lower the chance of developing a UTI, Dr. Burrows noted, including use of water-based lubricants during intercourse and avoiding scented hygiene products. Drinking lots of fluids and urinating soon after sexual activity can flush out bacteria from the urinary tract, Dr. Burrows added.
Dr. Burrows noted that the dietary supplement D-mannose, as well as concentrated forms of cranberry juice, can also minimize the chance of acquiring a UTI (Exp Ther Med 2020;20[4]:3399-3406).
But even with all precautions, sometimes UTIs will occur. Treatments like phages—viruses that target bacteria like E. coli—are promising alternatives to antibiotics (Eur Urol Focus 2024;10[5]:722-725).
“Phages were discovered over a century ago, and they were used to treat infections before antibiotics,” Dr. Burrows said. In the age of antimicrobial resistance, phages may soon be in the spotlight again.
The sources reported no relevant financial disclosures. Dr. Sokurenko presented his findings in a presentation at ASM Microbe 2025, in Los Angeles.