Increasing prevalence of ESBL production among Irish clinical Enterobacteriaceae from 2004 to 2008: an observational study

BACKGROUND: Extended spectrum β-lactamase (ESBL) producing Enterobacteriaceae infections are associated with delayed initiation of appropriate treatment, poor outcomes and increased hospital stay and expense. Although initially associated with healthcare settings, more recent international reports have shown increasing isolation of ESBLs in the community. Both hospital and community ESBL epidemiology in Ireland are poorly defined. METHODS: This report describes clinical and laboratory data from three hospitals over 4.5 years. All significant isolates of Enterobacteriaceae were subjected to standardized antimicrobial susceptibility testing and screening for ESBL production. Available patient data from hospital databases were reviewed. RESULTS: The database included 974 ESBL producing organisms from 464 patients. Urine and blood isolates represented 84% and 3% of isolates respectively. E. coli predominated (90.9%) followed by K. pneumoniae (5.6%). The majority of patients (n = 246, 53.0%) had been admitted to at least one of the study hospitals in the year prior to first isolation of ESBL. The overall 30-day all-cause mortality from the date of culture positivity was 9.7% and the 1 year mortality was 61.4%. A Cox regression analysis showed age over 60, male gender and previous hospital admissions were significant risk factors for death within 30 days of ESBL isolation. Numbers of ESBL-producing E. coli isolated from urine and blood cultures increased during the study. Urine isolates were more susceptible than blood isolates. Co-resistance to other classes of antimicrobial agents was more common in ESBL producers from residents of long stay facilities (LSF) compared with hospital inpatients who lived at home. CONCLUSIONS: This work demonstrates a progressively increasing prevalence of ESBL Enterobacteriaceae in hospital, LSF and community specimens in a defined catchment area over a long time period . These results will improve clinician awareness of this problem and guide the development of empiric antimicrobial regimens for community acquired bloodstream and urinary tract infections.