Increase in the Rate of Gut Carriage of Fluoroquinolone-Resistant Escherichia coli despite a Reduction in Antibiotic Prescriptions.

BackgroundFluoroquinolone use for urinary tract infections has been steadily declining. Gut microbiota is the main reservoir for uropathogenic Escherichia coli but whether the carriage of fluoroquinolone-resistant E. coli has been changing is unknown. MethodsWe determined the frequency of isolation and other characteristics of E. coli nonsuceptible to fluoroquinolones (at [&ge;]0.5 mg/L of ciprofloxacin) in 515 and 1605 E. coli-positive fecal samples collected in 2015 and 2021, respectively, from non-antibiotic-taking women of age 50+ receiving care in the Seattle area Kaiser Permanente Washington healthcare system. ResultsBetween 2015 and 2021 the prescription of fluoroquinolones dropped nearly three-fold in the study population. During the same period, the rates of gut carriage of fluoroquinolone-resistant E. coli increased from 14.4 % to 19.9% (P=.005), driven by a significant increase of isolates from the recently emerged, pandemic multi-drug resistant clonal group ST1193 (1.7% to 4.3%; P=.007) and those with an incomplete set of or no fluoroquinolone-resistance determining mutations (2.3% to 7.5%; P<.001). While prevalence of the resistance-associated mobile genes among the isolates dropped from 64.1% to 32.6% (P<.001), co-resistance to third generation cephalosporins has increased 21.5% to 33.1%, P=.044). ConclusionDespite reduction in fluoroquinolone prescriptions, gut carriage of fluoroquinolone-resistant uropathogenic E. coli increased with a rise of previously sporadic lineages and co-resistance to third generation cephalosporins. Thus, to reduce the rates of antibiotic resistant urinary tract infections, greater focus should be on controlling the gut carriage of resistant bacteria. Short summaryWhile prescription of fluoroquinolones dropped between 2015 and 2021, there was an increase in gut carriage of fluoroquinolone-resistant Escherichia coli among women of age 50+. Also, a rise of new resistant lineages and co-resistance to 3rd generation cephalosporins occurred.