Effectiveness of ceftazidime-avibactam for the treatment of infections due to Pseudomonas aeruginosa.

BACKGROUND: Clinical experience with ceftazidime-avibactam (CAZ-AVI) for treatment of infections due to multidrug or extremely resistant (MDR/XDR) Pseudomonas aeruginosa (P. aeruginosa) is limited. METHODS: A retrospective cohort study was conducted on patients with MDR/XDR P. aeruginosa infections treated with CAZ-AVI. The primary outcome was clinical cure by day 14, evaluated by logistic regression adjusted for the propensity score to receive CAZ-AVI as combination therapy. Secondary outcomes were 30-day all-cause mortality, 90-day recurrence, emerging CAZ-AVI resistance, and safety of therapy. RESULTS: Sixty-one first episodes of MDR/XDR P. aeruginosa infection were included. The most common source was lower respiratory tract infection (34.4%), 14.8% episodes developed bloodstream infection and 50.8% had sepsis at presentation. Ceftazidime-avibactam therapy was initiated at a median of 7.0 (interquartile range [IQR]: 3.5-12.0) days from symptom onset; it was used as combined therapy in 29 (47.5%) episodes. Clinical cure rate by day 14 was 54.1% and predictors of response were days to source control (adjusted odds ratio [aOR]: 0.84; 95% confidence interval [CI]: 0.72-0.98; P = 0.024), days until the initiation of CAZ-AVI therapy (aOR: 0.65; 95% CI: 0.49-0.86; P = 0.003), age (aOR: 1.07; 95% CI: 0.99-1.15; P = 0.066) and CAZ-AVI combination therapy (aOR: 0.02; 95% CI: 0.01-0.38; P = 0.009). Rates of 30-day all-cause mortality and 90-day recurrence were 13.1% and 12.5%, respectively. Emergence of drug resistance to CAZ-AVI was not detected. Treatment-related adverse events occurred in three episodes (4.9%). CONCLUSIONS: CAZ-AVI constitutes a valid alternative for the treatment of infections due to MDR/XDR P. aeruginosa.

Clinical and bacterial characteristics of Pseudomonas aeruginosa affecting the outcome of patients with bacteraemic pneumonia.

Few studies have assessed the clinical and bacterial characteristics of Pseudomonas aeruginosa (PA) bacteraemic pneumonia (BP) episodes. This study analysed all non-duplicate PA-BP episodes from a tertiary hospital in 2013-2017. Epidemiology, clinical data, antimicrobial therapy and outcomes were recorded. Whole-genome sequencing was performed on PA blood isolates. The impact on early and late overall mortality of host, antimicrobial treatment and pathogen factors was assessed by multivariate logistic regression analysis. Of 55 PA-BP episodes, 32 (58.2%) were caused by extensively drug-resistant (XDR) PA. ST175 (32.7%) and ST235 (25.5%) were the most frequent high-risk clones. ß-Lactamases/carbapenemases were detected in 29 isolates, including blaVIM-2 (27.2%) and blaGES type (25.5%) [blaGES-5 (20.0%), blaGES-1 (3.6%) and blaGES-20 (1.8%)]. The most prevalent O-antigen serotypes were O4 (34.5%) and O11 (30.9%). Overall, an extensive virulome was identified in all isolates. Early mortality (56.4%) was independently associated with severe neutropenia (aOR = 4.64, 95% CI 1.11-19.33; P = 0.035) and inappropriate empirical antimicrobial therapy (aOR = 5.71, 95% CI 1.41-22.98; P = 0.014). Additionally, late mortality (67.3%) was influenced by septic shock (aOR = 8.85, 95% CI 2.00-39.16; P = 0.004) and XDR phenotype (aOR = 5.46, 95% CI 1.25-23.85; P = 0.024). Moreover, specific genetic backgrounds [ST235, blaGES, gyrA (T83I), parC (S87L), exoU and O11 serotype] showed significant differences in patient outcomes. Our results confirm the high mortality associated with PA-BP. Besides relevant clinical characteristics and inappropriate empirical therapy, bacteria-specific genetics factors, such as XDR phenotype, adversely affect the outcome of PA-BP.