- During an 8-month period, 55 episodes of nosocomial bacteremia caused by Enterobacteriaceae species were identified in a tertiary medical center, of which 26 (47%) were caused by extended-spectrum beta lactamase (ESBL)-producing organisms. ESBL production was associated with resistance to aminoglycosides, fluoroquinolones, tetracycline and co-trimoxazole compared with non-ESBL-producing organisms (p < 0.01). By multivariate analysis, infection with ESBL-producing organisms was associated with previous antibiotic therapy and central venous catheter insertion and mortality was associated with heart failure, malignancy and a prolonged hospital stay. Nineteen (73%) patients infected with ESBL-producing organisms received adequate empirical antibiotic therapy and all 26 received adequate definitive therapy. The in-hospital mortality rate did not differ between patients infected with ESBL producers and those infected by non-ESBL-producing Enterobacteriaceae species [13/26 (50%) and 11/29 (38%), respectively] (p > 0.5).