What is “The Bacteria that Causes Bad Breath”?

Defining the Worst of the Worst

Since you were a child, you have heard advertising and comments about “the bacteria that causes bad breath.” Mouthwash advertising especially enjoys this phrase, and we even used it in our last blog article about helpful oral bacteria. So we often talk about this evil bad breath bacteria, but which one is it? Does it have a name? And how can our Placerville dentists help you avoid bad breath?

Identifying the Bacteria that Causes Bad Breath

First, dentists know that bad breath, or halitosis, is a symptom of the major gum diseases gingivitis and periodontitis. That’s because gum disease is basically the infection of your gums with harmful oral bacteria. And when those bacteria go to work on consuming the food you eat and destroying the tissues of your mouth, they produce stinky gases. Depending on the nature of the stench, you can even diagnose the likely bacterial culprit. Like a fine wine, beer or spirit, however, a lot of components may be creating the “flavor” of the halitosis, indicating more than one species of bacterium is hard at work destroying your gums and oral tissues. Since not too many dental workers are refined experts with the scents of dental malodours and the bacteria that make them, we are left with some educated guesses on the likely sources.

Many bacteria are implicated in gum disease, including:

  • Porphyromonas gingivalis
  • Treponema denticola
  • Actinobacillus actinomycetemcomitans (especially in children)
  • Bacteroides forsythus
  • Fusobacterium nucleatum
  • Prevotella intermedia

Of course, there are more — many more. One of the more interesting bacteria that creates a definite change in the odor of bad breath is Helicobacter pylori. This bacterium is seldom a pioneer or first colonizer of the gums, since it typically is found in the gut and is known for causing ulcers. When gum disease is already present, however, H. pylori can establish itself in the mouth and gums and adds to the strength of bad breath by increasing the amount of sulfurous gases in the mouth (especially the ones that produce the smell of rottenness).

Some types of halitosis, however, are caused not by bacteria, but by digestive or metabolic disorders. One example is trimethylaminuria, a result of the body being unable to digest certain nitrogen compounds. This syndrome produces a distinct smell of rotten fish. In cases such as these, a specialist in distinguishing dental scents (using what’s called the hedonic tone of specific smells) can diagnose the likely problem.

What Kind of Gases Cause Bad Breath?

The stinky gases that cause halitosis are generally categorized into three groups. These groups are:

Sulphur Compounds

  • Methyl mercaptan (the barnyard smell)
  • Hydrogen sulphide (the rotten egg smell)
  • Dimethyl sulphide (the cooked cabbage smell)


  • Cadaverine
  • Putrescine

These are the scents that come from decaying tissue and dead bodies; not a pleasant smell to have in your mouth!

Fatty Acids

  • Butyric acid (the smell of rancid fat and vomit)
  • Valeric acid (another cue in the scent of rancid food)
  • Propionic acid (the smell of body odor)

Needless to say, all of these chemicals are stinky. Combined together, they create an awful stench. Avoiding these scents requires more than just an after-dinner mint, stick of gum, or quick hit of drugstore mouthwash. It takes eliminating the gum disease and the bacteria that cause it.

So Which is the Worst?

Basically, if your mouth is invaded by any bacteria that attacks the gums, it’s “the worst” for your personal situation, and it is possible to actually test samples of the oral biome to figure out the likely culprit or culprits. But some bacteria are simply worse than others when it comes to making stink. 

One study compared two oral bacteria head-to-head, P. gingivalis and F. nucleatum, isolating which one was the “stink champion.” Researchers used both a halimeter, a device for analyzing the exact level of “bad” in bad breath, and their ever-present noses to rate the potency of bad breath smells in patients both with and without periodontitis. By comparing the relative presence or absence of P. gingivalis versus F. nucleatum, they determined that P. gingivalis was the worst of the two and “may play a key role in oral malodour production.” So for now, let’s give the title of “the bacteria that causes bad breath” to P. gingivalis.

If the American Dental Association decides to hold a March Madness-style competition to determine the worst of the worst, the Placerville Dental Group will let you know. Until then, please do not suffer with bad breath! There is always a cause and it can almost always be cured! Let us help you solve your halitosis once and for all with quality dentistry.


Submit a Comment

Your email address will not be published. Required fields are marked *

Our Dental Blog