A retrospective cohort study of high prevalence of ST131 among extended spectrum beta-lactamase producing E. coli among inpatients in the metropolitan Detroit area

Objectives: E. coli ST131 multi-locus sequence type (MLST) has been associated with extended spectrum beta-lactamase (ESBL) production, conferring antimicrobial resistance, with increased virulence and with healthcare-associated infection. The high prevalence of multidrug antimicrobial resistance in ESBL-producing ST131 E. coli infections creates unique challenges in the studying patient outcomes and analysis are required to study ST131 E. coli amongst a large population of ESBL-producers. Our objective was to determine the prevalence of ST131-type E. coli among previously characterized ESBL-producing isolates obtained from the metropolitan Detroit area and to conduct an epidemiologic analysis of risk factors and illness severity.;Methods: 377 ESBL-E. coli isolates were obtained from a previously conducted retrospective study of sequential clinical isolates obtained from the Detroit Medical Center health care system from February 2010 through July 2011. Isolate DNA was extracted and tested for ST131 characterization using a two-target multiplex PCR amplification (trpA and pabB). Patient demographics, medical history, clinical course, and illness severity were collected retrospectively from medical records, and E. coli susceptibility was obtained from the clinical laboratory. Predictors and outcomes of infection due to ST131 ESBL E. coli were compared to non-ST131 ESBL E. coli.;Results: 81.9% (n=309) of 377 tested isolates were positive for the ST131-specific pabB allele. Patients with ST131 versus non-ST131 EBSL E. coli were comparable with respect to age, race, and intensive care unit admission. 76.7% (n=283) of the ST131 isolates had CTX-M-15 and 13.8% (n=51) had CTX-M-14 present. However, the presence of CTX-M was not limited to the ST131 group, 63.3% (n = 38) of non-ST131 isolates had CTX-M-15 and 16.7 (n=10) had CTX-M-14 present.;Conclusion: we found out the high prevalence of ST131 among patients with E. coli infections. However, we detect no significant clinical difference between the infections caused by ST131 E. coli and non-ST131 E. coli.