Bloodstream infections caused by ESBL-producing E. coli and K. pneumoniae: risk factors for multidrug-resistance.

ABSTRACT

This prospective case-control study was conducted from October 2003 to June 2007 to evaluate risk factors for multidrug resistance among extended-spectrum-b-lactamase-producing Escherichia coli and Klebsiella spp. (ESBL-EK) isolates in blood cultures. All adult patients (>18 years old) whose blood cultures grew ESBL-EK during the study period were included. An ESBL-EK isolate was defined as MDR if it was resistant to at least one member of following two classes of antibiotics aminoglycosides (amikacin, gentamicin, or netilmycin) and fluoroquinolones (ofloxacin, or ciprofloxacin). Case patients were those with a MDR ESBL-EK isolate, and control patients were those with a non-MDR ESBL-EK isolate. A total of 94 bloodstream infections, including 37 (39,4%) bloodstream infections with ESBL-producing E. coli and 57 (60,6%) with ESBL-producing K. pneumoniae,in 86 patients were enrolled. Thirty episodes (31.9%) were due to MDR ESBL-EK. The only independent risk factor for MDR ESBL-EK was duration of hospitalization before bacteraemia (OR 3.88; 95% CI 1.55-9.71; p=0.004). The rate of multidrug resistance among ESBL-EK bloodstream isolates was high, and duration of hospitalization before bacteraemia was the only indeepended risk factor for the MDR ESBL-EK bloodstream infections.