Sterile fecal filtrate transplantation (FFT) effectively treated five cases of symptomatic chronic-relapsing Clostridium difficile infection, investigators reported.
The procedure restored normal bowel habits and eliminated symptoms through the end of the study – that is, for at least 6 months – in all patients, Stephan J. Ott, MD, and his associates wrote (Gastroenterology. 2019. doi: 10.1053/j.gastro.2016.11.010).
Proteome analyses did not identify proteins likely to explain this efficacy, but 16S rRNA gene sequencing did demonstrate diverse bacterial DNA signatures in the filtrates, and tests of virus-like particles yielded “a complex signature of macrophages,” Dr. Ott and his associates reported. Additional tests suggested that recipients’ microbiomes continued to change weeks after FFT. “This open-label series strongly suggests that FFT should be evaluated in a controlled setting in comparison with standard fecal microbiota transplantation,” the researchers concluded.
Fecal microbiota transplantation (FMT) effectively treats recurrent Clostridium difficile infection (CDI), but even “the most rigorous and costly donor screening procedures, or defined panels of bacteria, cannot exclude the risk of transferring unknown pathogens or undetectable functional characteristics within the living microorganisms to the recipient, including bacterial or viral risk factors for metabolic diseases, cancer, atopy, or autoimmunity,” the investigators wrote.
Therefore, they performed sterile FFT in five patients who were positive on at least two of three tests: enzyme-linked immunosorbent assay for C. difficile–specific glutamate dehydrogenase; C. difficile toxin enzyme-linked immunosorbent assay; and culture of toxin-producing C. difficile. Patients chose their own stool donors, who were then screened based on published guidelines (Clin Gastroenterol Hepatol. 2011;9[12]:1044-49). Next, “slurries” were prepared from donor stool and filtered with a custom-built air pressure filtration system, yielding a “light brown, clear liquid with a subjectively less unpleasant and intensive odor” than conventional FMT stool preparations. Bacterial cultures of these filtrates yielded no growth, whereas donor stool cultures showed profuse growth of aerobic and anaerobic bacterial colonies, Dr. Ott and his associates said.
Patients became symptom-free 2-4 days after undergoing FFT. Notably, one patient had previously undergone FMT, which led to acute fever and diarrhea and recurrence of baseline symptoms after 3 months. This patient did not develop fever or diarrhea after FFT, was symptom-free after 3 days, and remained symptom-free until the study ended 2 years later, the researchers said. All other patients also remained symptom-free through the end of the study, that is, for 6 months to more than 2 years.
Analyses of 16S rRNA revealed substantial longitudinal shifts after FFT that often were present by week 1 and remained stable until week 6, the investigators said. Further tests confirmed marked shifts in bacterial phylotypes and in their relative abundance over time. Repeated virus analyses of one patient also showed that the phageome shifted over time to resemble that of the donor.
Patients were between 49 and 75 years old, three were female and two were male, and all had received more than one antibiotic before their first episode of CDI. Antibiotics for CDI had included metronidazole, vancomycin, and rifaximin. Comorbidities included pseudomembranous colitis, renal failure, HIV infection, epilepsy, and chronic heart failure, and medical histories included recurrent diverticulitis with sigmoid resection, gastric carcinoma, and colon cancer.
“It is important to keep in mind that, in contrast to conventional FMT, transferring sterile FFT filtrates cannot be expected to establish a microbiota similar to that of the donor in the receiving patient,” Dr. Ott and his associates noted. Instead, bacterial DNA in the filtrate might trigger the re-establishment of the recipient microbiome, they said. Bacterial cell wall fragments or bacteriophages also might play a role, they added.
The German Excellence Cluster and CONARIS Research Institute AG supported the work. Dr. Ott reported having lectured for Allergosan. Two coinvestigators reported employment with CONARIS. A third coinvestigator reported shareholder relationships with CONARIS, Allergosan, Danone, and Nestle and lectureship compensation from Allergosan. The other eight coinvestigators had no relevant conflicts of interest.