High-Dose Tigecycline for Multidrug-Resistant Serratia Infections in Critically Ill Adults: A Systematic Review of Direct and Indirect Clinical Evidence

Evidence for high-dose tigecycline in severe multidrug-resistant Gram-negative infections comes mainly from non-Serratia cohorts.Its value in critically ill adults with resistant Serratia infection is uncertain.PubMed/MEDLINE, CENTRAL, and Consensus were searched up to July 17, 2026.Two evidence sets addressed high-dose tigecycline effectiveness, pharmacokinetics, and safety, and clinical and microbiological evidence for resistant Serratia.Study-level risk ratios were presented without pooling.Searches identified 2,294 records, and 36 studies reported in 37 publications were included.No study reported a verified high-dose regimen in confirmed resistant Serratia infection with a separately extractable organism-specific outcome.Six observational studies used the same high-dose and standard-dose definitions.Fixed 28-day or 30-day mortality risk ratios ranged from 0.34 to 1.30, and all 95% confidence intervals crossed 1.0.Clinical response favored high dose in two studies, with risk ratios of 1.73 (95% confidence interval: 1.22-2.46)and 1.48 (95% confidence interval: 1.08-2.02).Microbiological response favored high dose in two studies, with risk ratios of 1.75 (95% confidence interval: 1.09-2.81)and 1.92 (95% confidence interval: 1.12-3.28).No pooled estimate was calculated.High dose produced a greater fibrinogen decline in one cohort (-3.05 ± 1.67 versus -1.75 ± 1.90 g/L; p=0.038) and more hepatic or platelet abnormalities in another.Direct evidence for high-dose tigecycline in resistant Serratia infection is absent.Indirect studies show possible response benefits without a consistent survival advantage.Treatment decisions should consider infection site, susceptibility, active alternatives, and coagulation risk.By synthesizing both pathogen-specific studies and relevant indirect clinical evidence, this review aimed to provide a more comprehensive assessment of the potential role of high-dose tigecycline in critically ill adults with resistant S. marcescens infections.