Washed Microbiota Transplantation as a Rescue Therapy for Refractory Unidentified Pathogen Intestinal Infections:...

Unidentified pathogen intestinal infections (UPIIs) represent a severe clinical dilemma, characterised by clear signs of intestinal infection yet no identifiable causative pathogen, often leading to prolonged, antibiotic-refractory illness. A nationwide retrospective study based on the prospective cohorts from September 2015 to February 2025 was conducted in China to evaluate washed microbiota transplantation (WMT) on this challenging condition. Patients diagnosed with UPIIs and then underwent WMT were included. The primary outcome was the clinical response rate one month post-WMT. Finally, among the 81 included patients, 71.6% were bedridden, 46.9% required ICU admission and 51.9% developed multiple organ dysfunction syndrome. Diarrhoea was the primary symptom, and over half received ≥ 3 empirical antibiotics. Despite the challenges, WMT achieved a one-month clinical response rate of 63.0% and a cure rate of 43.2%. Multivariate analysis identified several baseline risk factors affecting WMT efficacy, including adverse events (AEs) related to WMT (β = 1.545, p = 0.026, OR = 4.690, 95% CI 1.208-18.206), total abdominal symptom scores (TASS) before WMT (β = 0.292, p = 0.047, OR = 1.340, 95% CI 1.004-1.788) and WHO performance status score ≥ 4 (β = 1.583, p = 0.031, OR = 4.867, 95% CI 1.160-20.423). The overall AEs rate was only 8.3% (18/216). A nomogram based on logistic regression [akaike information criterion (AIC) = 93.75] was developed to predict the clinical non-response at one month after WMT. The favourable clinical outcomes observed in this study provide cohort-based evidence on using WMT for treating refractory UPIIs. These findings implied that if WMT is available, earlier WMT may be beneficial for UPIIs.