Molecular characterization of intestinal bacteria in healthy cats and a comparison of the fecal bacterial flora between healthy cats and cats with inflammatory bowel disease (IBD)

Past studies characterizing the feline intestinal microflora have used traditional bacterial culture techniques. However, in recent years it has been recognized that the majority of intestinal bacteria are non cultivable. Therefore, the aim of this study was to describe the microflora along the intestinal tract in healthy cats using comparative 16S ribosomal DNA (16S rDNA) analysis. Intestinal content from the stomach, duodenum, jejunum, ileum, and colon was collected from 4 healthy cats and one specific pathogen free cat (SPF) and the bacterial composition was identified by direct sequencing of bacterial 16S rDNA amplicons. A predominant anaerobic microflora was observed in all evaluated segments of the intestine. Fourteen different bacterial orders were identified with the majority of all sequences classified in the class Clostridiales. Six different Clostridium clusters were identified with the majority of sequences affiliated with Clostridium cluster I. Comparative 16S rDNA analysis was also used to evaluate differences in the fecal microflora between healthy cats (n=6), cats with histopathologically confirmed inflammatory bowel disease (IBD; n=6), and cats with intestinal neoplasia (n=3). Compared to the IBD group, cats in the control group showed a significantly higher number of sequences classified as Firmicutes, Bacteroidetes, and Actinobacteria (p<0.0001). The control group had a significantly higher proportion of clones affiliated with Clostridium cluster XI, and a significantly lower proportion affiliated with cluster I (both p<0.0001). In the neoplasia group, the majority of sequences were classified in the phylum Firmicutes (97.9%) and clones were predominately affiliated with Clostridium clusters I and XI. These data indicate that the feline intestinal microflora is highly diverse and is comprised predominantly of anaerobic bacteria. Further studies are warranted to evaluate the clinical significance of the observed differences in intestinal microflora between healthy cats and cats with gastrointestinal disease.