Emergency Department Urinary Tract Infections Caused by Extended-Spectrum β-Lactamase-Producing Enterobacteriaceae: Many Patients Have No Identifiable Risk Factor and Discordant Empiric Therapy Is Common

Abstract

Study objective: Community-onset urinary tract infections (UTIs) caused by extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae, which are resistant to ceftriaxone and usually coresistant to fluoroquinolones, are increasing worldwide. We investigate and describe in detail UTIs caused by ESBL-producing Enterobacteriaceae in our emergency department (ED), and determine the proportion that occurred in patients without health care-associated risk factors and who received discordant initial antibiotic therapy.

Methods: At an urban public hospital in Northern California, microbiology staff prospectively reviewed ED urine culture results weekly for 1 year and presumptively identified ESBL-producing isolates by ceftriaxone plus ceftazidime resistance. For isolates associated with a clinical UTI, patient demographic and case clinical features were abstracted retrospectively. Health care-associated infections were defined by standard risk factors plus aged 65 years or older, bladder catheter, urologic procedure, functional dependence, or antibiotics in the previous 90 days. Community-associated infections were defined by absence of these. A subset of community-associated ESBL-producing Escherichia coli isolates underwent genotyping. Electronic health record query was used to determine the denominator of ED UTI patients who underwent urine culture during the study period.

Results: Between August 2016 and July 2017, there were 1,045 unique ED patients diagnosed with a UTI, whose specimens underwent culture. There were 62 ESBL-producing isolates (5.9%; 95% confidence interval [CI] 4.6% to 7.5%). Selected characteristics of the entire ESBL UTI cohort were median age 50 years, 37 (60%) patients were women, 28 (44%) Hispanic, 11 (18%) had been hospitalized in the previous 3 months, 19 (31%) had pyelonephritis, 49 (79%) of isolates were E coli, 44 (71%) were levofloxacin-resistant, and 24 (23%) nitrofurantoin-resistant. Initial antibiotic choice was discordant with isolate susceptibility in 26 of 56 cases (46%; 95% CI 33% to 60%), and the initial oral antibiotic prescred was discordant in 19 of 41 cases (46%; 95% CI 31% to 63%). Twenty-seven infections (44%; 95% CI 31% to 57%) were categorized as community-associated. Eight patients with community-associated infection were women younger than 50 years, with no comorbidities and no more than 1 UTI in the previous year. Of 12 community-associated E coli isolates tested, all were confirmed to harbor ESBL genes; the CTX-M1 β-lactamase gene was found in 8 (67%); 4 belong to genotype ST131.

Conclusion: At this single Northern California ED, greater than 5% of culture-proven UTI were caused by ESBL-producing Enterobacteriaceae, and in nearly half of cases there was no identifiable health care-associated risk factor. Levofloxacin co-resistance and discordant antibiotic therapy were common.