Clinical Efficacy and Safety of Omadacycline Versus Tigecycline in Treating Severe Pneumonia Caused by Carbapenem-Resistant Gram-Negative Bacilli: A Retrospective Cohort Study.

Objective: To investigate the clinical efficacy and safety of intravenous omadacycline compared to intravenous tigecycline in patients with severe pneumonia caused by carbapenem-resistant gram-negative bacilli (CRGNB), and to explore the factors influencing 28-day all-cause mortality.

Methods: Our retrospective analysis was conducted on adult patients with CRGNB-associated severe pneumonia who received intravenous omadacycline or tigecycline for at least 72 hours in the intensive care unit (ICU) between April 1, 2023, and March 31, 2025. The primary outcome was 28-day all-cause mortality, while secondary endpoints included clinical efficacy and microbiological clearance rates. Safety was also assessed. Logistic regression analysis was used to identify factors associated with 28-day all-cause mortality.

Results: A total of 80 patients with CRGNB-associated severe pneumonia were enrolled, including 43 in the omadacycline group and 37 in the tigecycline group. Compared with the tigecycline group, there was no statistically significant difference in 28-day mortality (χ² = 2.882, p = 0.090) or microbiological clearance rate (58.14% vs 48.65%, p = 0.501) in the omadacycline group. However, the omadacycline group showed a significantly higher clinical efficacy rate (72.09% vs 43.24%, p = 0.012) and a markedly lower incidence of adverse events (4.65% vs 24.32%, p = 0.020). Multivariate logistic regression analysis revealed that combination therapy with β-lactams was an independent predictor of reduced 28-day mortality, whereas central venous catheterization and baseline C-reactive protein (CRP) levels were independently associated with increased 28-day mortality.

Conclusion: Our study found that omadacycline is comparable to tigecycline in clinical effectiveness for the treatment of CRGNB-associated severe pneumonia, while exhibiting a better safety profile. Novel tetracyclines may be used in combination with β-lactams for the treatment of severe pneumonia caused by CRGNB.