Submitted to: The ISME Journal: Multidisciplinary Journal of Microbial Ecology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/4/2011
Publication Date: N/A
Citation: Interpretive Summary: Ovine foot rot is an infectious, contagious disease of sheep that causes severe lameness and economic loss from decreased flock production. Foot rot is an important infectious animal disease that affects international and domestic agricultural economies. The disease is characterized by dermatitis of the interdigital skin of the hoof that sometimes affects the horns of sheep. Lameness can be severe and may affect all four feet. Dichelobacter (Bacteroides) nodosus is thought to be the essential causal pathogen. Next-generation nucleotide pyrosequencing technologies and quantitative-PCR were utilized to more thoroughly characterize the bacterial populations found at the hoof-skin interface of sheep by comparing healthy versus diseased sheep. Twenty-five (25) bacterial genera were detected using these techniques and interestingly Dichelobacter nodosus was detected in both healthy and diseased sheep. Also, sheep with an interdigital dermatitis had greater numbers of the bacterium than healthy sheep or those with highly virulent foot rot. Consequently, knowledge of the bacterial ecology of this malady may lead to improved therapies based on control of secondary bacteria that may be important to causing disease other than just Dichelobacter nodosus.
Technical Abstract: We report the first study of the bacterial microbiome of ovine interdigital skin based on 16S rRNA by pyrosequencing and conventional cloning with Sanger-sequencing. Ovine foot rot is an infectious, contagious disease of sheep that causes severe lameness and economic loss from decreased flock production. Three sheep flocks were selected for study, one a flock with no signs of ovine footrot or interdigital dermatitis, a second flock with interdigital dermatitis alone and a third flock with both interdigital dermatitis and footrot. The sheep were classified as having either healthy interdigital skin (H) and interdigital dermatitis (ID) or virulent footrot (VFR). The ovine interdigital skin bacterial community varied significantly by flock and clinical condition. The diversity and richness of operational taxonomic units was greater in tissue from sheep with ID than H or VFR-affected sheep. Actinobacteria, Bacteriodetes, Firmicutes and Proteobacteria were the most abundant phyla comprising 25 genera. Peptostreptococcus, Corynebacterium and Staphylococcus were associated with H, ID and VFR, respectively. Sequences of Dichelobacter nodosus, the causal agent of ovine footrot, were not amplified because of mismatches in the 16S rRNA universal forward primer (27F). A specific real-time PCR assay was used to demonstrate the presence of D. nodosus, which was detected in all samples including the flock with no signs of ID or VFR. Sheep with ID had significantly higher numbers of D. nodosus than those with H or VFR feet.