In the last year, the National Institute of Dental Research awarded two separate research grants that, together, set a new standard for studying oral pathogens. Over the next three years, these studies will sequence the genomic DNA of the periodontal bacterium Actinobacillus actinomycetemcomitans (Aa) and the opportunistic fungus, Candida albicans. The sequencing data produced by these studies will be instrumental in understanding the genetic mechanisms responsible for virulence and drug resistance in these pathogens, and may lead to novel approaches for preventing or eradicating infections.
The National Institute of Dental Research awarded a grant to Dr. David W. Dyer at the University of Oklahoma to determine the sequence of the 2.2 million nucleotide base pairs that make up the genome of Aa.
Aa was selected for the project primarily because of its important role in periodontal disease. Aa is thought to be the cause of localized juvenile periodontitis (LJP), a condition that affects 70,000 children and adolescents each year in the United States. LJP is a chronic inflammatory infection of the gingiva and underlying bony tissues, and there is no effective prevention. Treatment involves surgical or mechanical removal of diseased tissues ("scaling and planing"), coupled with antibiotic therapy. Despite such extensive treatment, the condition can still recur. Without treatment, LJP can result in tooth loss by the age of 20.
The pathology of Aa is poorly understood. It is known that Aa attaches to and
invades human epithelial cells and produces toxins that can kill or maim human
cells. However, little is known about other virulence factors harbored by the
organism, and current NIDR-supported projects focus on specific factors rather
than the total spectrum of pathologic mechanisms. Determining the complete
nucleotide sequence of Aa will eventually yield a more complete picture of
Contact: Wayne Little
NIH/National Institute of Dental and Craniofacial Research