Baseline oral microbiome associated with post-living donor liver transplant early complications within 6 months.

Oral dysbiosis is noted in liver cirrhosis. This may play a role in post-liver transplantation (LT) outcomes. This study aimed to assess the baseline oral microbiome and its association with early complications (ECs) within 6 months after LT. This prospective longitudinal study included 94 cirrhotic recipients (CRs) and their living donors. Patients were managed with a standardized immunosuppressive regimen and monitored for 6 months post-LT EC rejection, infection, biliary complications (BCs), and death. Pre-LT and post-LT saliva samples were processed for bacterial sequencing, qPCR validation, and cytokine profiling. The association between microbial abundance and EC was assessed. At baseline, CR exhibited a lower Bacteroidota and a higher abundance of Bacillota compared with donors. Streptococcaceae and Veillonellaceae were enriched in CR compared with their respective donors ( p <0.05, each). On follow-up, post-LT ECs were noted in 35/94 patients. Prominent Bacillota , Bacteroidetes , and Actinomycetota were noted at baseline in those who developed rejection, infection, and BCs, respectively. Species-level analysis, followed by qPCR validation, revealed complication-specific baseline microbial signatures: Escherichia marmotae (FC 3.9) for rejection, Prevotella salivae (FC 71) for infections, and Rothia (FC 301) and Lactobacillus rhamnosus (FC 51) in BCs. The baseline enrichment of Prevotella_7_sp2 , Klebsiella pneumoniae , and Staphylococcus was associated with sepsis-related mortality. Recipients with post-LT EC showed pro-inflammatory links ( Prevotella with IL-2, Streptococcus with IL-8). Baseline oral microbiome profiles were differentially abundant among individuals who developed post-LT ECs. Incorporating microbial signatures may enable noninvasive risk stratification after LT.