Different Clinical Characteristics and Impacts of Carbapenem-Resistance on Outcomes Between Acinetobacter Baumannii and Pseudomonas Aeruginosa Bacteraemia: A Multicentre Prospective Observational Study

Background: Carbapenem-resistance (CR) causes poor clinical outcomes and has limited treatment options. We aim to evaluate the differences in clinical characteristics and impact of carbapenem-resistance on outcomes between Acinetobacter baumannii (ABA) and Pseudomonas aeruginosa (PAE) bacteraemia. Methods: We prospectively identified all patients with ABA and PAE bacteraemia in 10 hospitals over a 1-year period and collected their detailed clinical information. Treatment failure was defined as all-cause 30-day mortality, persistent bacteraemia, or recurrence within 30 days.Results: We included 304 ABA and 241 PAE bacteraemia cases. CR was detected in 216 ABA (71%) and 55 PAE (23%). Treatment failure was significantly higher in CR-ABA than in CR-PAE (60.6% vs. 34.5%, P = 0.001). Multivariate analyses were stratified by patient data according to CR and the appropriateness of empirical therapy. For ABA patients, severe sepsis or septic shock and high Pitt bacteraemia score were independent risk factors for treatment failure in the inappropriate empirical antibiotics group. Pneumonia was a significant risk factor in the appropriate group. For PAE patients, hospital-acquired infection and high Pitt bacteraemia score were independent risk factors for treatment failure in both groups. CR was an independent risk factor in ABA for treatment failure in both the inappropriate (adjusted odds ratio [aOR]: 6.17, 95% confidence interval [CI]: 1.13-33.75, P = 0.036) and appropriate empirical treatment groups (aOR: 4.15, 95% CI: 1.16-14.84, P = 0.029), but not for patients with PAE bacteraemia. Conclusions: We demonstrated significant differences in the clinical characteristics and impact of CR on the clinical outcomes between ABA and PAE bacteraemia. Our findings suggest that different approaches may be needed to treat ABA and PAE bacteraemia.