Phenotypic and proteomic characterization of treponemes associated with bovine digital dermatitis

Authors: Nally, Jarlath; Hornsby, Richard; Alt, David; WHITELEGGE, JULIAN - University Of California

Submitted to: Veterinary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/2019
Publication Date: 5/30/2019
Citation: Nally, J.E., Hornsby, R.L., Alt, D.P., Whitelegge, J.P. 2019. Phenotypic and proteomic characterization of treponemes associated with bovine digital dermatitis. Veterinary Microbiology. 235:35-42. https://doi.org/10.1016/j.vetmic.2019.05.023.
DOI: https://doi.org/10.1016/j.vetmic.2019.05.023

Interpretive Summary: Digital dermatitis (DD) is a multifactorial polymicrobial infectious disease originally described in dairy cattle, but is increasingly recognized in beef cattle, sheep, and more recently, elk and goats. Bovine digital dermatitis (BDD) is a global disease that results in significant economic losses every year due to lameness associated with decreased milk yield. No single bacterial aetiology of BDD has been identified but most commonly, bacteria associated with BDD comprise multiple species and phylotypes from the genus Treponema. However, despite the large number of different treponemes detected in lesions of BDD, few isolates have actually been cultured, and few of those have been characterized any further. In this study, a novel strain of T. brennaborense, was cultured and identified from a lesion of BDD, as well as another strain of T. phagedenis, strain 1452. T. brennaborense has different growth requirements compared to T. phagedenis and displays rapid motility when observed by dark field microscopy. The outer membrane protein profile of several strains of treponemes was characterized to identify components that will provide for the future evaluation of outer membrane components in understanding pathogenic mechanisms of BDD and the development of diagnostics and vaccines.

Technical Abstract: Bovine digital dermatitis (BDD) is a multifactorial polymicrobial infectious disease associated with multiple species and phylotypes of treponemes. However, despite the abundance of molecular signatures for treponemes that are identified in bovine lesions, relatively few isolates are cultured, and even fewer have been characterized at the level of protein expression. Here we report the successful isolation and characterization of novel strains of T. brennaborense and T. phagedenis from cases of BDD in Iowa dairy cows, and compare them to a well characterized strain of T. phagedenis, and the type strain of the more recently recognized T. pedis. Propagation of T. brennaborense was only possible at room temperature in Cooked Meat Medium, and not in oral treponeme enrichment medium at 37oC as used for T. phagedenis and T. pedis. A prominent and rapid motility observed by dark field microscopy readily differentiates T. brennaborense from other treponemes. The highly motile T. brennaborense strain 11-3 has an identical enzymatic profile to that of the only other isolate of T. brennaborense to be cultured from a lesion of BDD. Outer membrane protein profiles of each strain were compared by 2-D gel electrophoresis, and the five most abundant proteins in each strain were identified by mass spectrometry. All identified proteins are predicted to have signal peptides. Results identified outer membrane proteins specific to each strain including predicted membrane lipoproteins, ABC transporters and, as yet, uncharacterized proteins. Collectively, our results provide for the identification and characterization of outer membrane components of multiple phylotypes of treponemes associated with BDD which can facilitate development of vaccines and diagnostics in our efforts to eradicate the disease.