Chronic laminitis is associated with potential bacterial pathogens in the laminae

A common sequella of chronic laminitis in horses is repeated abscesses with variable lameness and drainage. It is unclear whether the exudate represents the debridement phase of a non-septic inflammatory process involving clearance of laminar tissue damaged during the acute episode of laminitis, or a response to a microbial infection developed by ascent of microbes from the environment to the tissue via the white line. The objective of this study was to evaluate the possibility that an undiagnosed microbial infection in laminar tissue is present in laminar tissue collected from chronically laminitic horses without an active hoof abscess. Methods to collect laminar tissue, aseptically, from control (non-laminitic) horses and those with chronic/recurrent laminitis are described. Laminae homogenates were evaluated for the presence of bacteria. Bacteria were identified using biochemical tests and sequencing of 16S rRNA and virulence genes. Laminae from chronically laminitic horses revealed 100-fold higher levels (P=0.002) of bacteria compared to control, non-laminitic horses. Although environmental organisms were identified, potential pathogens were identified. Included were Gram positive bacteria, Brevibacterium luteolum, coagulase-negative Staphylococcus spp. as well as Gram negative bacteria, enterohemorrhagic Escherichia coli and Alcaligenes faecalis. Further research is warranted to evaluate the role of bacteria in equine chronic laminitis.