Resistance Patterns of Escherichia coli in Women with Uncomplicated Urinary Tract Infection Do Not Correlate with Emergency Department Antibiogram

Abstract

Background: Urine cultures are not always performed for female Emergency Department (ED) patients with uncomplicated urinary tract infection (UTI). Accordingly, hospital, and even ED-specific, antibiograms might be skewed toward elderly patients with many comorbidities and relatively high rates of antimicrobial resistance, and thus do not accurately reflect otherwise healthy women. Our ED antibiogram indicates Escherichia coli resistance rates for ciprofloxacin, levofloxacin, and trimethoprim-sulfamethoxazole (TMP-SMX) of 42%, 26%, and 33%, respectively.

Objectives: This study aims to compare resistance rates of urinary E. coli from otherwise healthy women with uncomplicated UTI and pyelonephritis in the ED to rates in our ED antibiogram.

Methods: Females > 18 years old with acute onset of urinary frequency, urgency, or dysuria with pyuria identified on urinalysis (white blood cell count > 10/high-power field) were prospectively enrolled in the ED of an urban, academic medical center. Exclusion criteria indicating a complicated UTI were consistent with Infectious Diseases Society of America guidelines. Susceptibility patterns of E. coli to ciprofloxacin, levofloxacin, and TMP-SMX in the study group were compared to our ED antibiogram.

Results: Forty-five patients grew E. coli. Pyelonephritis was suspected in nine (20%) subjects. Compared with the ED antibiogram, significantly lower rates of resistance to ciprofloxacin (2% vs. 42%, p < 0.001), levofloxacin (2% vs. 26%, p < 0.001), and TMP-SMX (16% vs. 33%, p = 0.016) were observed. Six patients grew non-E. coli uropathogens. All were susceptible to both levofloxacin and TMP-SMX.

Conclusions: ED antibiograms may overestimate resistance rates for uropathogens causing uncomplicated UTIs. In cases where nitrofurantoin cannot be used, fluoroquinolones and possibly TMP-SMX may remain viable options for treatment of uncomplicated UTI and pyelonephritis in women.

Keywords: antibiogram; antibiotic resistance; community-acquired infection; pyelonephritis; urinary tract infection.