Fecal microbiota transplantation is a highly effective therapy for recurrent Clostridium difficile infection (CDI).
However, transferring undefined living bacteria entails uncontrollable risks for infectious and metabolic or malignant diseases, particularly in immunocompromized patients.
Dr Stefan Schreiber and colleagues from Germany investigated whether sterile fecal filtrates that contain bacterial debris, proteins, antimicrobial compounds, metabolic products, and oligonucleotides/DNA, rather than intact microorganisms, are effective in patients with CDI.
The researchers performed a clinical case series to investigate the effects of fecal filtrate transfer (FFT) in 5 patients with symptomatic chronic-relapsing CDI at the Department of Internal Medicine I at the University Hospital Schleswig-Holstein.
Patients were followed up for at least 6 months and for up to 33 months.
Stool was collected from 5 donors selected by the patients, and fully characterized according to fecal microbiota transplantation standards.
The team sterile-filtered the samples to remove small particles and bacteria.
The team of doctors then transferred the filtrate was transferred to patients in a single administration via nasojejunal tube.
Fecal samples were collected from patients before and at 1 week and 6 weeks after FFT.
Microbiome, virome, and proteome profiles of donors and patients were compared.
In all 5 patients, the doctors observed that FFT restored normal stool habits, and eliminated symptoms of CDI for a minimum period of 6 months.
Proteome analyses of selected FFT filtrates showed no obvious protein candidates associated with therapeutic efficacy.
The team noted that 16S ribosomal RNA gene sequencing detected diverse bacterial DNA signatures in the filtrates.
Analysis of virus-like particles from a filtrate found to reduce symptoms of CDI showed a complex signature of bacteriophages.
The doctors also analyzed bacterial phylogeny and virome profiles of fecal samples from recipients that indicated longitudinal changes in microbial and viral community structures after FFT.
Dr Schreiber's team comments, "A preliminary investigation of 5 patients with CDI shows that transfer of sterile filtrates from donor stool (FFT), rather than fecal microbiota, can be sufficient to restore normal stool habits and eliminate symptoms."
"This finding indicates that bacterial components, metabolites, or bacteriophages mediate many of the effects of fecal microbiota transplantation, and that FFT might be an alternative approach, particularly for immunocompromized patients."