A team of researchers from The Forsyth Institute and the University of Michigan School of Dentistry have determined that certain bacteria found on the tongue are associated with halitosis and others with fresh-smelling breath.
As reported in the current Journal of Clinical Microbiology, the researchers used gene sequencing techniques to compare bacteria found on the tongues of individuals with halitosis and those with fresh breath. "In each of six individuals with halitosis, we found several species that were not found in those with fresh breath," said Bruce Paster, Senior Member of the Staff at Forsyth. "Conversely, in five individuals with fresh breath, we identified species not generally found in those with halitosis.
While not all samples taken from halitosis sufferers had the same bacterial makeup, the researchers determined that the same bacteria¿Streptococcus salivarius, Rothia mucilaginosa, and a previously uncharacterized strain of Eubacterium--were the most prevalent species on the tongues of subjects with fresh breath. The most prevalent bacterium found in such individuals¿Streptococcus salivarius¿was found in only one of the individuals with malodorous breath, and at very low levels.
The six species most associated with halitosis in the current study were: Atopobium parvulum; a phylotype of Dialister; Eubacterium sulci; a phylotype of the as yet uncultivated phylum TM7; Solobacterium moorei; and a phylotype of Streptococcus.
"These findings would suggest that certain bacteria are associated with bad breath, and that others, the normal microflora, protect against it," Paster said. It is well known that bacterial species that normally colonize specific sites of the healthy body are able to block the colonization of potentially harmful bacteria.
The current study is part of an ongoing effort to determine genetic sequences for all species that colonize the oral cavity. While the current study population was small, the findings have been confirmed in subsequent forthcoming research on a larger group of subjects, Paster said.
Although the bacteria of the tongue have long been implicated as a major source of odor production in subjects with halitosis, the bacterial composition of the tongue is still not well known. In part, this is because such bacteria are difficult to recover, grow in culture, and to identify by traditional biochemical tests. In the current molecular analysis of tongue scrapings, the scientists found 92 bacterial species, of which 29 have never before been described in the scientific literature. Paster cautioned that with an estimated 700 bacterial species in the oral cavity, there are likely to be some 100 species yet to be identified. "This means that there may well be additional species responsible for good and bad breath."
Background on halitosis.
Halitosis, or oral malodor, is a common complaint of up to one-third of the general population. It can arise from the sinuses, gastrointestinal tract, ingested food, lungs, and, most frequently, the mouth. Oral production of malodorous substances is most common associated with by-products of bacterial metabolic degradation and occurs on oral surfaces, in periodontal pockets, and, especially, on the surface of the back of the tongue. These bacterial products result from microbial fermentation of proteins, peptides, and mucins found in saliva, blood, gingival crevicular fluid, dead epithelial cells, and residual food retained on the oral surfaces. Halitosis has also been correlated with the presence and severity of periodontal disease and by the amount of coating on the tongue. Such coating varies in thickness depending on the topography of the tongue and the length of the filiform papillae found on its surface. Coating is ordinarily composed of saliva, blood, dead epithelial cells, residual food debris, and, primarily, bacteria.
Oral malodor is often effectively treated by reducing the bacterial load on the tongue and teeth through twice-daily tooth brushing with fluoride toothpaste and daily tongue debridement with a toothbrush or other mechanical device, either alone or in combination with the use of anti-microbial mouth rinses such as chlorhexidine.
In forthcoming research, the team will report on successful use of other types of rinses and therapy that appear to diminish the presence of bacteria believed responsible for halitosis, and to enhance the presence of those which appear to protect against it.
Team members based at the Forsyth Institute include: Bruce J. Paster, PhD, and Floyd E. Dewhirst, DDS, PhD, both Senior Members of the Staff in the Department of Molecular Genetics; and Patricia M. Mitchell, Alice M. Lee, and Lauren N. Stokes, all research assistants. Team members from the University of Michigan School of Dentistry in Ann Arbor include: Christopher Kazor, DDS, PhD, Research Fellow in Biologic and Materials Science and Adjunct Clinical Professor of Periodontics, Prevention and Geriatrics; and Walter J. Loesche, DMD, PhD, Marcus Ward Professor Emeritus of Dentistry and Professor Emeritus of Microbiology and Immunology. In addition to their Forsyth appointments, Drs. Paster and Dewhirst are associate professors of oral and developmental biology at the Harvard School of Dental Medicine.
The Forsyth Institute is an independent, nonprofit research institute focused on oral, craniofacial and related biomedical science.
(The article, "Diversity of Bacterial Populations on the Tongue Dorsa of Patients with Halitosis and Healthy Patients," is available online at http://jcm.asm.org or from the contacts listed.