Clinical outcomes of patients hospitalized in internal medicine wards adequately treated for bloodstream infections caused by NDM-producing Klebsiella pneumoniae. Results from a real-life retrospective multi-center study in an endemic area.

Background: New Delhi metallo-beta-lactamase (NDM)-producing Klebsiella pneumoniae (NDM-Kp) represents a growing challenge for modern medicine.

Objectives: To assess real-life clinical outcomes in patients adequately treated in Internal medicine units (IMUs) for bloodstream infections (BSI) caused by NDM-Kp.

Methods: A two-years retrospective study was conducted recruiting 30 consecutive adult patients with NDM-Kp BSI treated with an adequate definitive antibiotic therapy (27 aztreonam plus ceftazidime/avibactam; 3 cefiderocol) in three Italian IMUs located in a highly endemic area.

Results: Mean age of patients was 75.3 years, mean Charlson Comorbidity Index (CCI) 7.5. All the patients had rectal colonization. Thirty-day mortality rate was 46.7%; 78.6% of patients who died received an adequate empiric therapy. Non-survivors had mean age, CCI and SOFA score significantly higher compared to survivors (80.1 vs. 71.2, p = 0.036; 8.6 vs. 6.6, p = 0.047; 5.9 vs. 4, p = 0.043, respectively). The percentage of survivors was significantly higher among the 13 cases with community-acquired than in the 17 with hospital-acquired BSI (76.9% vs. 35.3%, p = 0.024). In the multivariate penalized logistic regression analysis, age, CCI, SOFA score and hospital-acquired BSI onset were identified as independent predictors of mortality.

Conclusion: This study provides real-life data on clinical outcomes regarding old and highly multimorbid patients hospitalized in IMU for BSI caused by NDM-Kp, showing a very high 30-day mortality even in case of adequate treatment.