Evaluation of the clinical impact of de-escalated versus non-de-escalated antibiotics for the treatment of methicillin-susceptible staphylococcus aureus pneumonia in critically ill patients admitted to intensive care units: a multicenter cohort study

Critically ill patients are at a higher risk of developing infections and related complications, which can lead to death. Each additional day of antipseudomonal β-lactam use increases the risk of resistance; therefore, de-escalation is highly recommended to improve antibiotic use. To our knowledge, there are limited studies that have evaluated the clinical impact of de-escalation in critically ill patients with proven Methicillin-Susceptible Staphylococcus aureus (MSSA) pneumonia alone. Therefore, our study aimed to assess the clinical impact of the de-escalation strategy compared with the non-de-escalation strategy in critically ill patients with proven MSSA pneumonia. This multicenter retrospective cohort study was conducted in three tertiary hospitals from January 2016 to July 2021. Adult critically ill patients admitted to the intensive care unit with proven MSSA respiratory culture who received antibiotics with anti-MSSA activity were screened for eligibility. Eligible patients were categorized into two groups according to their de-escalation status: De-escalated and Non-de-escalated. The De-escalation was defined as the reduction of the antimicrobial activity spectrum of antibiotics by switching to a narrower-spectrum agent that targets MSSA. The primary outcome was treatment failure rate, while other outcomes were considered secondary. Propensity score (PS) matching was applied at a 1:1 ratio, and multivariate regression analyses were utilized as appropriate. After PS matching (1:1), 58 patients were included in the study (29 patients in non-deescalated vs 29 patients in de-escalated). The treatment failure rate was significantly higher in the de-escalated group compared to the non-de-escalated (OR 16.98; 95% CI (3.304–87.225), p = 0.0007). In contrast, no significant differences were found in 30-day mortality, hospital and ICU length of stays, ventilator-free days, ICU readmission rate, or MSSA infection recurrence rate. Our results showed that de-escalation of antibiotics in critically ill patients with confirmed MSSA pneumonia was associated with significantly higher rate of treatment failure while no significant differences were observed in the other clinical outcomes. These findings highlight the need for prospective studies to better inform safe and effective de-escalation strategies in this population.