Approximately 6% of all patients presenting at an emergency department (ED) during a 1-year period with a urinary tract infection (UTI) were diagnosed with an extended-spectrum b-lactamase (ESBL)-producing Enterobacteriaceae infection, according to new findings published in the Annals of Emergency Medicine. Many of these patients also lacked an identifiable risk factor for a multidrug-resistant UTI and had frequently been treated with discordant antimicrobial agents.

The investigators note UTIs acquired in the community that are caused by resistant ESBL-producing Enterobacteriaceae are increasing worldwide. In the current study, the proportion of UTIs caused by these pathogens was investigated among patients seen at an urban ED in Northern California.

During a 1-year period, a total of 1045 patients diagnosed with a UTI were seen in the ED, and in this group, 62 ESBL-producing isolates (5.9%; 95% CI, 4.6%-7.5%) were identified. Some of the characteristics of this patient subgroup included: median age 50 years, 37 (60%) were women, 28 (44%) were Hispanic, 11 (18%) had been hospitalized in the previous 3 months, 19 (31%) had pyelonephritis, 49 (79%) isolates were Escherichia coli, 44 (71%) were levofloxacin resistant, and 24 (23%) were nitrofurantoin resistant. The initial course of antibiotic therapy was discordant with the isolate’s susceptibility in nearly half of the participants, 26 of 56 cases (46%; 95% CI, 33%-60%). The initial oral antibiotic prescribed was also discordant in 19 of 41 cases (46%; 95% CI, 31%-63%).  A total of 27 of the UTIs (44%; 95% CI, 31%-57%) were categorized as community associated; 8 women in this subgroup were younger than 50 years of age, had no comorbidities, and had not experienced more than 1 UTI during the previous year. Of 12 community-associated E coli isolates tested, all were confirmed as harboring ESBL genes; the CTX-M1 b-lactamase gene was found in 8 (67%) and 4 were genotype ST131.

This study did have a few limitations. Primarily, as a single-center study, external validity is the greatest of these limitations. Threats to external validity included that antibiotic susceptibility is known to vary between geographic locations, and that cultures were performed selectively and were slightly more likely to be obtained in patients perceived to be at risk for resistance. This may have led to an overestimate of the actual prevalence of UTIs caused by ESBL-producing Enterobacteriaceae.

The results of this study concur with those of the 2 most recent studies and therefore, “raise serious concern in regard to trends in antibiotic resistance among uropathogens from community-onset infections, and have implications for future ED practice and research,” note the investigators, adding that in some locations in the United States, “fluoroquinolone resistance rates in urinary isolates already exceeds the 20% level at which this class should not be used.” Investigators recommend “[w]ide use of urine culture even in uncomplicated cystitis, combined with a reliable follow-up system” as an effective way to address these concerns.

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Frazee BW, Trivedi T, Montgomery M, Petrovic DF, Yamaji R, Riley L. 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 [published online July 3, 2018]. Ann Emerg Med. doi: 10.1016/j.annemergmed.2018.05.006