Bacterial ecology, continued

To Beat Bad Breath, Keep the Bacteria in Your Mouth Happy: Scientific American

There seems to be a lot of interest suddenly in scientific circles about how bacterial ecology (particularly in the gut) affects the general health of  humans.  Here's another instalment of the story, but this time starting at the mouth:

Bacterial geneticists contributing to the Human Microbiome Project, funded by the National Institutes of Health, have so far identified about 1,000 species of bacteria that commonly inhabit human mouths. Yet one person's particular mix of “bacterial colleagues,” as Rosenberg calls them, is probably quite different from another's. “Each person has maybe 100 to 200 of those bacterial species colonizing their mouth at any given time,” says Wenyuan Shi, a microbiologist at the University of California, Los Angeles.

During birth our previously sterile mouth picks up some of our mother's bacteria, and in childhood we quickly acquire new microbial colonizers. Studies suggest that a preschooler's population of mouth microbes most closely mimics his or her primary caregiver's. As the years go on, diet, stress, illness, antibiotics and other forces can shift the demographics of an individual's microbial community—and change its collective aroma. When bacteria that release smelly compounds dominate, chronic bad breath may be one of the consequences.

Many current treatments do not improve oral ecology—in fact, they might make matters worse. Although some mouthwashes merely mask unpleasant odors, alcohol-based rinses sold in drugstores and prescription rinses containing chlorhexidine or other antiseptics target all oral bacteria, stinky and otherwise. Shi says that approach has several drawbacks. A chlorhexidine rinse, for example, may improve breath for as long as 24 hours but can temporarily change the taste of food. In one study, 25 percent of subjects experienced a tingling or burning sensation on the tongue after a week of use. Heavy use of rinses with alcohol can dry out the mouth, sometimes exacerbating bad breath. Further, wiping out too many of the mouth's native bacteria could disrupt the usual checks and balances, making way for opportunistic species responsible for gum disease and other infections to move in and take over.

 The article goes on to discuss new treatments being tested to give a more permanent "cure" by changing the bacterial mix in the mouth.  For example:

Other teams are investigating whether probiotics rife with a gram-positive bacterial strain known as Streptococcus salivarius K12 can fight halitosis. A common resident of the mouth and respiratory tract, S. salivarius K12 is benign and known to produce substances that deter harmful bacteria. In a recent study by researchers in New Zealand and Australia, volunteers gargled with a chlorhexidine mouthwash to clear their palate of many native bacteria and subsequently sucked on lozenges laced with K12. Seven and 14 days later they had much sweeter breath. Presumably K12 outcompeted its foul-smelling kin, opening up niches for less offensive species.

 I wonder if protracted kissing with someone with good breath can help too!