Lab culture plates for testing E. coli sensitivity and resistance to antibiotics. Credit: Sokurenko Lab/UW Medicine
Key points:
- Despite a six-year decline of prescribing the antibiotic ciprofloxacin, ciprofloxacin-resistant E. coli actually increased.
- The researchers found that the rate of a particularly virulent strain, ST1193, rose during the study period.
- The findings are consistent with theoretical models indicating that, once a drug-resistant form of E.coli emerges, it will continue to spread.
After a year of not taking any antibiotics, women over the age of 50 actually had increased presence of gut-colonizing ciprofloxacin-resistant E. coli, as opposed to the expected decrease.
According to a study by Washington researchers, after a nearly threefold drop in prescriptions for the antibiotic ciprofloxacin between 2015 and 2021, the rates of ciprofloxacin-resistant E. coli bacteria circulating in the community did not decline.
Ciprofloxacin and similar drugs in its class were once the most prescribed antibiotic for urinary tract infections. In 2015, recommendations discouraged broad use of this class of drugs for uncomplicated urinary tract infections, partly due to rising resistance. So the question is, did the reduction help? The answer seems to be no.
In the study, published in Communications Medicine, the scientists worked with Seattle-area women over 50 years of age. They examined participants’ positive samples to determine which antibiotic-resistant strains of E. coli were present.
The researchers found that the rate of a particularly virulent strain, ST1193, rose during the study period. Together with E. coli strain ST131-H30, these strains are the major causes of a global pandemic of multi-drug-resistant urinary tract infections among all women. If ST1193 makes its home in more people’s guts, the situation could lead to more urinary tract infections with this virulent strain, regardless of the curbing of fluoroquinolones prescriptions.
Another strain with a troubling increase in the participant samples was ST69, known to more frequently cause urinary tract infections in children.
The findings are consistent with theoretical models indicating that, once a drug-resistant form of E.coli emerges, it will continue to spread by taking up long-term residence in individuals’ gut microbiomes.
The study authors suggest scientists prioritize discovering better ways to control drug-resistant E. coli’s ability to colonize the gut before it causes more serious infections.