1438. Escherichia coli (EC) ST131-H30 Clonal Group is Associated with Antimicrobial Resistance, Illness Severity, Host Compromise, and Non-Cure among Patients with Bacteriuria

BACKGROUND: EC sequence type ST131 is the leading cause of extraintestinal EC infections, and accounts for most fluoroquinolone (FQ)-resistant and extended-spectrum β-lactamase (ESBL)-producing EC clinical isolates. The ST131-H30 subclone (H30) is responsible for most antimicrobial resistance within ST131; however, H30’s impact on clinical outcomes is poorly defined. We compared empiric treatment patterns and clinical outcomes of patients with bacteriuria caused by ST131 vs. non-ST131 EC, and by H30 vs. non-H30 EC strains. METHODS: Phylogroups, ST131, H30, and CTX-M-type β-lactamase genes were detected by PCR for 142 non-duplicate EC isolates collected prospectively from hospitalized or emergency-department-attending adults with monomicrobial bacteriuria at a Boston academic medical center (August 2013–January 2014). Clinical and microbiologic data were collected retrospectively from electronic health records. Baseline characteristics, empiric treatment, and clinical cure rates were compared between ST131 vs. non-ST131, and H30 vs. non-H30, patient cohorts. RESULTS: Of 142 patients with EC bacteriuria, most (76%) were female and elderly (mean age 65.2 ± 21.2 years). Overall, 35% of isolates were ST131, of which 80% (39/49) were H30. Compared with other isolates, H30 isolates demonstrated a higher frequency of ESBL production (33% vs. 8%; P < 0.001) and FQ resistance (90% vs. 8%; P > 0.001). Patients with H30 isolates (vs. non-H30 isolates) were older (mean 73.4 ± 13.6 vs. 62.1 ± 22.7 years; P < 0.01), had higher median (interquartile range [IQR]) APACHE II scores (10 [4] vs. 8 [9.5]; P = 0.01), more commonly had underlying complicating conditions (100% vs. 83%; P = 0.03) and received in vitro-inactive empirical treatment (26% vs. 3%; P < 0.01), and had a numerically lower clinical cure rate (84% vs. 96%; P = 0.08). In contrast, patients with ST131 vs. non-ST131 isolates had similar median [IQR] APACHE II scores (9 [5] vs. 8 [9]), frequencies of symptomatic UTI (61% vs. 70%) and underlying complicating conditions (24% vs. 19%), and clinical cure rates (87% vs. 95%). CONCLUSION: Among patients with EC bacteriuria, the ST131-H30 subclone was associated significantly with ESBL production, FQ resistance, illness severity, host compromise, and numerically lower clinical cure rates in symptomatic UTI. DISCLOSURES: Elizabeth B. Hirsch, PharmD, Merck: Grant/Research Support, Research Grant; Nabriva Therapeutics: Advisory Board; Paratek Pharmaceuticals: Advisory Board.