Risk factors for and clinical outcomes of bloodstream infections caused by extended-spectrum beta-lactamase-producing Klebsiella pneumoniae

OBJECTIVE: To evaluate risk factors and treatment outcomes of bloodstream infections caused by extended-spectrum beta-lactamase-producing Klebsiella pneumoniae (ESBL-KP). DESIGN: Retrospective case-control study. Stored blood isolates of K pneumoniae were tested for ESBL production by NCCLS guidelines, double-disk synergy test, or both. SETTING: A 1,500-bed, tertiary-care university hospital and referral center. PATIENTS: Sixty case-patients with bacteremia due to ESBL-KP were compared with 60 matched control-patients with non-ESBL-KP. RESULTS: There were no significant differences in age, gender, APACHE 11 score, or underlying diseases between the groups. Independent risk factors for infections caused by ESBL-KP were urinary catheterization, invasive procedure within the previous 72 hours, and an increasing number of antibiotics administered within the previous 30 days. Complete response rate, evaluated 72 hours after initial antimicrobial therapy, was higher among control-patients (13.3% vs 36.7%; P =.003). Treatment failure rate was higher among case-patients (35.0% vs 15%; P =.011). Overall 30-day mortality rate was 30% for case-patients and 28.3% for control-patients (P =.841). Case-patients who received imipenem or ciprofloxacin as a definitive antibiotic had 10.5% mortality. The mortality rate for initially ineffective therapy was no higher than that for initially effective therapy (9.1% vs 11.1%; P =1.000), but statistical power was low for evaluating mortality in the absence of septic shock. CONCLUSION: For K pneumoniae bacteremia, patients with ESBL-KP had a higher initial treatment failure rate but did not have higher mortality if antimicrobial therapy was appropriately adjusted in this study with limited statistical power.