Mistletoe alert: more bacteria discovered in the mouth

NEW YORK, Dec 24 (Reuters Health) -- Something else to think about when you pucker up under the mistletoe: Scores of previously undiscovered bacteria have been found living in the crevices between the teeth and gums of humans, researchers report.

``Our data suggest that a significant proportion of the resident human bacterial flora (in the mouth) remain poorly characterized, even within this well studied and familiar microbial environment,'' according to Dr. David Relman and his team at Stanford University School of Medicine in California.

The investigators used both new molecular biology and traditional bacterial culture methods to examine the bacterial makeup of the subgingival (below the gums) crevice in humans.

By analyzing the DNA of microbial samples collected from the mouth, scientists detected 31 types of organisms not previously reported, the results indicate, representing more than 52% of the types isolated.

In fact, the authors report, classical bacterial culture methods detected another six previously unreported bacterial types.

Even with the availability of newer gene-typing methods, Relman and colleagues note, both approaches are necessary to provide a full picture of the mouth bacterial census. About 83% of the new types were discovered only by molecular methods, ''whereas (10.5% were discovered only by cultivation; the remaining 6.5% were discovered by both approaches,'' they write.

This analysis of the bacterial population of the mouth probably still underestimates its actual diversity, they explain, as it used just one specimen from a single individual.

And before you grab the mouthwash -- the clinical relevance of the findings remains unclear. Some of the microorganisms may simply be just passing through, ``transient residents acquired from the environment,'' the investigators suggest, while others ''may be critical for maintenance of ecosystem stability and oral health or may be occasional (causes of disease).''

What is clear is that the mouth contains a significantly broader diversity of bacterial types than ever before recognized, the scientists conclude.

SOURCE: Proceedings of the National Academy of Sciences 1999;96:14547-14552.