Christopher Johnston, PhD

Oral health and systemic health are closely linked. Bacteria that cause inflammation and disease within the mouth are increasingly being found in association with extra-oral infections and systemic disease. Christopher Johnston is interested in the virulence mechanisms of oral bacterial species and determining how bacteria from the mouth establish themselves at other sites in the body to cause inflammation and disease. “The sooner we identify and understand the mechanisms used by these pathogens, the sooner we can design targeted therapeutic interventions to prevent disease” says Johnston. Accordingly, his lab has three major focus areas: bacterial virulence, genetic engineering and bacteriophage therapy.

One area of Johnston’s research relates to Prevotella intermedia, a major oral pathogen associated with periodontitis, endodontic infections and oro-facial gangrene. This organism is increasingly found in association with extra-oral infections including nasopharyngeal and respiratory infections during exacerbations of Cystic Fibrosis (CF); a progressive genetic disease characterized by chronic bacterial infections and inflammation of the lungs. He is working with the Rittling lab to determine the mechanism used by a novel P. intermedia cytotoxin (LtxP), during colonization and infection of the mouth and the CF lung.

Prevotella intermedia, like the vast majority of bacteria that can be grown in a laboratory, remains genetically intractable, beyond the power of genetics for elucidating function or engineering for human use. Accordingly, Johnston is interested in synthetic biology and the development of broadly applicable methods that can be used in genetic engineering of oral and extra-oral bacteria of relevance to human health and disease.

An additional interest of the lab is the application of phage therapy. Bacteriophage, the viruses that attack bacteria, are widely distributed in the oral cavity. By identifying and engineering bacteriophage from the mouth, Johnston hopes to develop targeted bio-control molecules against persistent infections in both oral and systemic disease.


Cork Institute of Technology, Cork, Ireland, BSc, 2008, Applied Bioscience, Cell and Molecular Biology
Cork Institute of Technology, Cork, Ireland, PhD, 2013,  Molecular Microbiology