Looking for Stenotrophomonas maltophilia treatment: in vitro activity of ceftazidime/avibactam alone and in combination with aztreonam.

During the Sars-Cov-2 pandemic, Stenotrophomonas maltophilia (S.maltophilia) secondary pulmonary infections have increased, especially in critically ill patients, highlighting the need for new therapeutic options. Trimethoprim-sulfamethoxazole (SXT) is the treatment of choice but the increase of resistant strains or adverse drug reactions limited its clinical use. Recently ceftazidime/avibactam (CZA) has been approved for the treatment of multi drug resistant (MDR) Gram-negative bacteria infections, including hospital acquired pneumonia. The aim of this study was to evaluate the in vitro activity of ceftazidime/avibactam (CZA) alone and in combination with aztreonam (ATM) against S. maltophilia clinical isolates by E-test method. Susceptibility of SXT and levofloxacin (LEV) was also investigated. Our results showed 22% of resistance to CZA, 2% to SXT and 26% to LEV. CZA in combination with ATM demonstrated synergistic activity against 86% of the strains, including all those resistant to CZA. The combination of CZA with ATM provides a new therapeutic option for the treatment of severe respiratory infections in critically ill patients.

Impact of a Multistep Bundles Intervention in the Management and Outcome of Gram-Negative Bloodstream Infections: A Single-Center "Proof-of-Concept" Study.

Background: This is a "proof-of-concept" study aiming to evaluate the impact of a multistep bundles intervention in the management and outcomes of patients with gram-negative bloodstream infections (GN-BSIs). Methods: This was a single-center, quasi-experimental design study. In the pre-phase (January 2019 to May 2020), patients were retrospectively enrolled. During the post-phase (June 2020 to September 2021), all patients were prospectively enrolled in a nonmandatory 3-step bundles intervention arm including (i) step 1: imaging to detect deep foci of infection, follow-up blood cultures and procalcitonin monitoring; (ii) step 2: early targeted antibiotic treatment and surgical source control; (iii) step 3: discontinuation of antibiotics within 7-10 days in case of uncomplicated BSI. Patients were followed up to 28 days from BSI onset. The primary outcome was 28-day mortality. Results: A total of 271 patients were enrolled: 127 and 144 in the pre- vs post-phase, respectively. Full application of step 1 (67% vs 42%; P < .001), step 2 (83% vs 72%; P = .031), and step 3 (54% vs 2%; P < .001) increased in the post-phase. Overall, the intervention reduced 28-day mortality (22% vs 35%, respectively; P = .016) and the median duration of total (11 vs 15 days; P < .001) and targeted (8 vs 12 days; P = .001) antibiotic therapy. Finally, the multivariate Cox regression confirmed the independent protective effect of adherence to step 1 (adjusted hazard ratio [aHR], 0.36; 95% CI, 0.20-0.63) and step 2 (aHR, 0.48; 95% CI, 0.29-0.81) on risk of 28-day mortality. Conclusions: Clinical management and outcomes of patients with GN-BSIs may be improved by providing a pre-established multistep bundles intervention.