Reappraisal of Pseudomonas aeruginosa hospital-acquired pneumonia mortality in the era of metallo-β-lactamase-mediated multidrug resistance: a prospective observational study

INTRODUCTION: Hospital-acquired pneumonia (HAP) due to Pseudomonas aeruginosa is associated with high mortality rates. The metallo-β-lactamases (MBLs) are emerging enzymes that hydrolyze virtually all β-lactams. We aimed to assess P. aeruginosa HAP mortality in a setting of high-rate MBL production METHODS: A prospective cohort study was performed at two tertiary-care teaching hospitals. A logistic regression model was constructed to identify risk factors for 30-day mortality. RESULTS: One-hundred and fifty patients with P. aeruginosa HAP were evaluated. The 30-day mortality was 37.3% (56 of 150): 57.1% (24 of 42) and 29.6% (32 of 108) for patients with HAP by MBL-producing P. aeruginosa and by non-MBL-producing P. aeruginosa, respectively (relative risk, 1.93; 95% confidence interval (CI), 1.30–2.85). The logistic regression model identified a higher Charlson comorbidity score (odds ratio, 1.21; 95% CI, 1.04–1.41), presentation with severe sepsis or septic shock (odds ratio, 3.17; 95% CI, 1.30–7.72), ventilator-associated pneumonia (odds ratio, 2.92; 95% CI, 1.18–7.21), and appropriate therapy (odds ratio, 0.24; 95% CI, 0.10–0.61) as independent factors for 30-day mortality. MBL production was not statistically significant in the final model. CONCLUSION: MBL-producing P. aeruginosa HAP resulted in higher mortality rates, particularly in patients with ventilator-associated pneumonia, most probably related to the less frequent institution of appropriate antimicrobial therapy. Therapeutic approaches should be reviewed at institutions with a high prevalence of MBL.