Phenotypic and proteomic characterization of treponemes associated with bovine digital dermatitis

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 37 °C as used for T. phagedenis and T. pedis. A prominent and rapid motility is observed by T. brennaborense under dark-field microscopy. 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.