Porphyromonas pigment in bovine footrot: implications in pathophysiology and treatment

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Anaerobic bacteria grow in the absence of oxygen. While they are being found to increasingly contribute to disease in many settings the study of anaerobes is grossly under-represented due in part to the difficulty in working with these organisms. My lab has been involved in studying these infections and we employ as a model sytem bovine footrot (BFR) caused by Porphyromonas levii, a black-pigmented anaerobe that synergistically contributes to the disease. BFR serves as a perfect model system for anaerobic infection and is perceived by Canadian farmers as noteworthy, a significant irritation in conventional animal production, as well as a major cause of animal discomfort and lameness. As animal welfare concerns intensify, and as current uses of antibiotics are scrutinized more closely, infectious diseases such as BFR will have much larger impact. Understanding BFR more fully is critical as the pressures to restrict large-scale antibiotic use (current control method) increase in society. BFR infection is intellectually intriguing because of its complex polymicrobial nature, its ubiquity in the world's cattle, the acute pyogenic character (ie. pus formation typifies BFR) of the response in affected animals, and its suitability as a model of bacterial synergism, hence providing insight in other such infections. Critical are the nature and function of white blood cells such as neutrophilic leukocytes (PMN) and macrophages in resolution, or lack of resolution, of BFR (ie. dead/dying PMN are the primary constituent of pus). The severity of BFR unquestionably hinges on a complex interplay of the bacteria including their repertoire of virulence attributes (such as the black pigment) and the cattle host, including the animals' immune cell responses (PMN and macrophages). My lab specializes in examining these phenomena. For some time now we have been alone in evaluation of the virulence of P.levii. We have studied bovine PMN and macrophages, in conjunction with our interests and capability in the antimicrobial resistance research, for years. This research proposal coalesces these interests through the unique role bacterial pigment plays in infection, pathophysiology, and resistance to treatment.