Predictors of Mortality in Bloodstream Infections Caused by Klebsiella pneumoniae Carbapenemase-Producing K. pneumoniae: Importance of Combination Therapy

BACKGROUND: The spread of Klebsiella pneumoniae (Kp) strains that produce K. pneumoniae carbapenemases (KPCs) has become a significant problem, and treatment of infections caused by these pathogens is a major challenge for clinicians. METHODS: In this multicenter retrospective cohort study, conducted in 3 large Italian teaching hospitals, we examined 125 patients with bloodstream infections (BSIs) caused by KPC-producing Kp isolates (KPC-Kp) diagnosed between 1 January 2010 and 30 June 2011. The outcome measured was death within 30 days of the first positive blood culture. Survivor and nonsurvivor subgroups were compared to identify predictors of mortality. RESULTS: The overall 30-day mortality rate was 41.6%. A significantly higher rate was observed among patients treated with monotherapy (54.3% vs 34.1% in those who received combined drug therapy; P = .02). In logistic regression analysis, 30-day mortality was independently associated with septic shock at BSI onset (odds ratio [OR]: 7.17; 95% confidence interval [CI]: 1.65-31.03; P = .008); inadequate initial antimicrobial therapy (OR: 4.17; 95% CI: 1.61-10.76; P = .003); and high APACHE III scores (OR: 1.04; 95% CI: 1.02-1.07; P < .001). Postantibiogram therapy with a combination of tigecycline, colistin, and meropenem was associated with lower mortality (OR: 0.11; 95% CI: .02-.69; P = .01). CONCLUSIONS: KPC-Kp BSIs are associated with high mortality. To improve survival, combined treatment with 2 or more drugs with in vitro activity against the isolate, especially those also including a carbapenem, may be more effective than active monotherapy.