Urinary Tract Infections due to Multidrug-Resistant Enterobacteriaceae: Prevalence and Risk Factors in a Chicago Emergency Department

Background. Selection of empiric antibiotics for urinary tract infections (UTIs) has become more challenging because of the increasing rates of multidrug-resistant Enterobacteriaceae (MDRE) infections. Methods. This retrospective study was conducted to determine antibiotic resistance patterns, risk factors, and appropriate empiric antibiotic selection for MDRE UTIs. Adult patients seen in the Emergency Department (ED) with Enterobacteriaceae UTIs during 2008-2009 were identified from review of microbiology records. MDRE were defined as organisms resistant to at least 3 categories of antibiotics. Results. There were 431 eligible patients; 83 (19%) had MDREUTIs. Resistance rates for individual antibiotics among MDRE UTIs were significantly greater than non-MDRE UTIs: levofloxacin, 72% versus 14%; TMP-SMX, 77% versus 12%; amoxicillin-clavulanate, 35% versus 4%; nitrofurantoin, 21% versus 12%, and ceftriaxone, 20% versus 0%. All Enterobacteriaceae isolates were susceptible to ertapenem (MIC <= 2mg/L). Independent risk factors for MDREUTI were prior fluoroquinolone use within 3 months (adjusted odds ratio (aOR) 3.64; P = 0.001), healthcare-associated risks (aOR 2.32;P = 0.009), and obstructive uropathy (aOR 2.22;P = 0.04). Conclusion. Our study suggests that once-daily intravenous or intramuscular ertapenem may be appropriate for outpatient treatment of ED patients with MDRE UTI.