Mouth as the gateway to your body

A key to plaque formation, said Yiping W. Han, a professor of periodontics at Case Western Reserve University is one of the most abundant and persistent bacterium that inhabits the mouth, Fusobacterium nucleatum.

She's found that the bacterium not only helps contagions attacking your teeth and gums but enables disease and infection to spread throughout the body.

Han's research is in the upcoming book, Oral Microbial Communities: Genomic Inquiry and Interspecies Communication, edited by Paul E. Kolenbrander, which will be published later this year.

One of the most common oral diseases is gingivitis and one of the main causes of gingivitis is the formation of plaque, which is facilitated by F. nucleatum. The presence of F. nucleatum can increase infection rate of gingivitis by a factor of two or more.

Other diseases caused by or enabled by the bacteria, include periodontitis, peritonsillar, and orofacial abscesses.

But, the damage is not solely localized in the mouth. From the mouth F. nucleatum can travel through the bloodstream and invade other organs.

Through oral diseases, F. nucleatum can get into the bloodstream and cause pregnancy complications, including miscarriage, preterm birth, and stillbirth. The bacteria colonize in amniotic fluid, which stimulates an inflammatory response that harms the fetus.

This bacterium is also found in lung, liver, spleen, blood, abdominal, and obstetrical and gynecological abscesses and infections.

Han explains that "attachment is the very first step…. and Fusobacterium adhesion A (FadA) was found to be involved in binding."

Binding is a crucial step for establishing an infection in the mouth and the body.
Han found that a galactose-binding lectin is involved in the attachment process.

Invasion also requires the involvement of actins, microtubules, signal transduction, protein synthesis, and energy metabolism of the epithelial cell. Invasion is a way bacteria gain entry to the host cell and resides close to the cell's membranes.

During oral infection, the bacteria can increase in number as much as 10,000 times, making it one of the dominant anaerobic species in the disease site.

Bacteria do not colonize the mouth randomly. Colonization is well organized and occurs in predictable successions. The mouth will be inhabited by the first bacteria colonizer followed by the second until it is colonized by F. nucleatum.

This process facilitates the formation of a bioflim, which helps the bacteria colonies adhere to the surface of the teeth.

"It's like the cream in an Oreo cookie, which holds the parts in place," Han explains.

F. nucleatum interacts with a number of other bacteria and facilitates their invasion of the host's epithelial and endothelial cells. They evade the host immune system and bind to a variety of host cells to be used to transport bacteria into deeper tissues.

By knowing the attachment process and how this bacterium binds, we can develop more effective drugs, Han said. But, more research is needed to determine the exact role F. nucleatum plays and the mechanism that enables it to interact with other bacteria.

As for now, Han suggests that we "brush, floss, and see a dentist."

Provided by Case Western Reserve University