Characteristics and outcomes of patients treated with tigecycline for MDR gram-negative infections: a retrospective cohort study

Introduction Multidrug-resistant (MDR) gram-negative pathogens pose a major therapeutic challenge, particularly in settings with limited antimicrobial options. Tigecycline is frequently used as salvage therapy. However, evidence regarding the optimal tigecycline regimen, whether used as monotherapy or in combination, remains uncertain. This study aimed to describe the characteristics, clinical, and microbiological outcomes of these cases. Methods Retrospective, single-center study of adult hospitalized patients treated with tigecycline for MDR Acinetobacter baumannii , extended-spectrum β-lactamase (ESBL)-producing Escherichia coli , and ESBL- or Carbapenem-Resistant Enterobacterales Klebsiella pneumoniae . Patients were categorized into tigecycline monotherapy or combination therapy groups. The primary outcomes were clinical success and 30-day mortality. Multivariable logistic regression was used to identify predictors of outcomes. A sensitivity analysis excluding bloodstream and urinary tract infections was performed due to pharmacokinetic limitations of tigecycline. Results Two hundred eighty were included; 116 (41.4%) received tigecycline monotherapy and 164 (58.6%) received combination therapy. Patients receiving combination therapy had higher illness severity and higher intensive care unit admissions. Overall clinical success was achieved in 53.2% of patients with a higher rate in the monotherapy group (64.7%, p = 0.001), and 30-day mortality was 26.1%. After adjustment, tigecycline monotherapy was not independently associated with clinical success or mortality. Sensitivity analyses excluding bloodstream and urinary tract infections showed consistent results. Conclusion In this real-world cohort of severely ill patients with MDR gram-negative infections, no outcome advantage was observed with tigecycline combination therapy after adjustment. Clinical outcomes were primarily driven by illness severity and infection characteristics rather than treatment strategy.