Analysis of Antibiotic Switches for UTI Treatment at a Quaternary Academic Medical Center

Objectives: Urinary tract infections (UTI) are the second most common cause of outpatient antibiotic prescriptions, of which as many as ~65% may be inappropriate. Given worsening global antibiotic resistance, antimicrobial stewardship aims to use the shortest effective duration of the most narrow-spectrum, effective antibiotic for patients with specific urinary symptoms and laboratory testing consistent with UTI. Antibiotic switching is indicated when resistance to first-line antibiotics is revealed on microbiological testing. This study sought to analyze antibiotic treatment failures as measured by antibiotic switching for treatment of urinary tract infections (UTI) in ambulatory care.

Methods: For this retrospective cohort study, 599 encounters during July 2019 bearing a diagnostic code for UTI/cystitis at a quaternary academic medical center were reviewed. Demographics, urinary and microbiological testing, and symptoms endorsed at presentation were extracted from the medical record. Antibiotic prescriptions, follow-up, and alternative diagnoses for each encounter were also catalogued. Antibiotic switching was defined as dispensing of an antibiotic of a different group within 28 days of the index encounter.

Results: Of 599 UTI encounters, 411 has associated antibiotic prescriptions. Of these, 15% (63/411) were switched to alternative antibiotics within 28 days. Within this group, only 24% (15/63) had acute urinary symptoms in the context of a positive culture. Thirteen of these (21%) had negative urinary cultures, yet still underwent antibiotic switching. In 25% of cases (16/63), patients were switched to a first-line antibiotic from a second- or last-line antibiotic, indicating there was no initial contraindication to appropriate antibiotic selection. An additional 10 subjects (16%) were switched to antibiotics with poor efficacy in UTI (e.g., ampicillin). While patients who were subjected to antibiotic switching tended to be older (64 vs. 58 years of age, p =0.09), there were no differences in the organisms isolated in positive cultures, the proportions of bacteria on urinalysis, or rates of acute UTI symptoms (e.g., dysuria). There were, however, significant differences in the proportion of subjects with positive urine cultures who underwent switching (79%) in comparison to subjects who did not (56%, p< 0.001).

Conclusions: The rate of antibiotic switching for UTI is far higher in this population than that documented for respiratory illnesses, occurring even in the absence of cystitis-like symptoms or positive cultures. Fewer than one-third of subjects received an appropriate first-line antibiotic, yet about one-quarter were subsequently switched to a first-line medication, supporting previous data documenting poor compliance with and awareness of consensus guidelines. More than 75% of subjects subjected to antibiotic switching lacked either symptoms or cultures consistent with UTI, supporting previous studies demonstrating high rates of UTI misdiagnosis. Given the profound potential contribution to antibiotic resistance, these findings highlight the need for improved diagnostic and prescribing accuracy for UTI.