Prophylactic antibiotics used to prevent recurrent urinary tract infections were associated with increased antimicrobial resistance on urine culture but were not linked to a statistically significant increase in hospital admissions for antibiotic-resistant infections, according to a large retrospective cohort study.
Researchers analyzed data from the Secure Anonymised Information Linkage (SAIL) Databank in Wales, including 48,297 women aged 18 years or older with recurrent urinary tract infections (UTIs) between 2015 and 2020. Of these, 839 initiated prophylactic antibiotics—most commonly nitrofurantoin, trimethoprim, or cefalexin—while the remainder did not.
The primary outcome was hospital admission with an antibiotic-resistant infection within 12 months. This occurred in approximately 1.4% of women who did not receive prophylaxis compared with 1.9% of those who did, a difference that was not statistically significant. Similarly, there was no statistically significant difference between groups in hospital admissions for antibiotic-resistant urinary tract infections.
In contrast, differences were observed in microbiological outcomes. Patients receiving prophylactic antibiotics were more likely to have antibiotic-resistant bacteria detected on urine culture. Resistance to at least one antibiotic occurred in about 31% of the prophylaxis group compared with 24% of those not receiving prophylaxis. Resistance to two or more antibiotics was also higher, occurring in roughly 22% versus 14%, respectively.
These findings suggest that although resistant organisms were more frequently identified in laboratory testing among patients receiving prophylaxis, this was not associated with a statistically significant increase in serious infections requiring hospital admission over the study period.
The number needed to harm was estimated at approximately 13 to 15 patients for one additional case of antibiotic resistance detected on urine culture.
When a single uropathogen was identified, Escherichia coli was the most common organism.
The study distinguishes between microbiological resistance and clinical outcomes. Although prior evidence supports the effectiveness of prophylactic antibiotics in reducing recurrence of UTIs, this analysis focused on resistance outcomes and did not assess recurrence rates.
The results may inform shared decision-making discussions, particularly when balancing symptom prevention against the risk of antibiotic resistance.
Limitations of the study include its observational design, which introduces the possibility of residual confounding, as well as potential variability in urine culture testing and resistance reporting. Misclassification of prophylactic antibiotic use and other design factors may also have influenced results.
Disclosures: One author reported receiving research-related diagnostic devices from Llusern Scientific, GADx, and Sysmex Astrego. Another reported royalties, advisory roles, and expert testimony payments. All other authors reported no competing interests.
Source: The Lancet
