Fecal microbiota transplantation (FMT) is becoming a more widely used technology 
for treatment of recurrent Clostridum difficile infection (CDI). While previous 
treatments used fresh fecal slurries as a source of microbiota for FMT, we 
recently reported the successful use of standardized, partially purified and 
frozen fecal microbiota to treat CDI. Here we report that high-throughput 16S 
rRNA gene sequencing showed stable engraftment of gut microbiota following FMT 
using frozen fecal bacteria from a healthy donor. Similar bacterial taxa were 
found in post-transplantation samples obtained from the recipients and donor 
samples, but the relative abundance varied considerably between patients and 
time points. Post FMT samples from patients showed an increase in the abundance 
of Firmicutes and Bacteroidetes, representing 75-80% of the total sequence 
reads. Proteobacteria and Actinobacteria were less abundant (< 5%) than that 
found in patients prior to FMT. Post FMT samples from two patients were very 
similar to donor samples, with the Bacteroidetes phylum represented by a great 
abundance of members of the families Bacteroidaceae, Rikenellaceae and 
Porphyromonadaceae, and were largely comprised of Bacteroides, Alistipes and 
Parabacteroides genera. Members of the phylum Firmicutes were represented by 
Ruminococcaceae, Lachnospiraceae, Verrucomicrobiaceae and unclassified 
Clostridiales and members of the Firmicutes. One patient subsequently received 
antibiotics for an unrelated infection, resulting in an increase in the number 
of intestinal Proteobacteria, primarily Enterobacteriaceae. Our results 
demonstrate that frozen fecal microbiota from a healthy donor can be used to 
effectively treat recurrent CDI resulting in restoration of the structure of gut 
microbiota and clearing of Clostridum difficile.