Which gut bacteria can contribute to halitosis?

Halitosis, gut bacteria & TMA

Several gut bacteria are known to produce trimethylamine (TMA).

Trimethylamine is an organic compound that has a strong, fishy odor. It is produced in the body through the digestion of certain nutrients, particularly choline and carnitine, which are found in foods like eggs, liver, fish and legumes.

Gut bacteria play a key role in converting these nutrients into TMA by metabolising dietary compounds like choline and carnitine. TMA is then absorbed into the bloodstream and processed by the liver enzyme called flavin-containing monooxygenase 3 (FMO3).

Here are some key bacterial genera and species involved in TMA production.

Key TMA-Producing bacteria

1. Enterobacteriaceae Family

   1. Escherichia coli – Some strains have been identified as TMA producers

   2. Klebsiella pneumoniae – Is also known to produce TMA from dietary choline

2. Clostridiaceae Family

   1. Clostridium sporogenes – Can metabolise choline to produce TMA

   2. Clostridium difficile – Is known for its role in gut infections, and can also produce TMA

3. Desulfovibrionaceae Family

   1. Desulfovibrio species – Is involved in the production of TMA in the gut

4. Ruminococcaceae Family

   1. Ruminococcus gnavus – Can metabolise choline and contribute to TMA production

5. Bacteroidaceae Family

   1. Bacteroides species – Some species are capable of producing TMA

Mechanism of TMA Production

Gut bacteria produce TMA through the enzymatic breakdown of choline, carnitine, and betaine. Here’s how

• Choline – Many gut bacteria possess the enzyme choline TMA-lyase, which breaks down choline into TMA and acetaldehyde

• Carnitine – Gut bacteria can convert carnitine to TMA via similar enzymatic pathways

• Betaine? – Some studies indicate that betaine can be converted to TMA by gut bacteria, but this is not considered the primary pathway for TMA generation

Influence of Diet and Gut Microbiota Composition

The production of TMA in the gut is influenced by

1. Dietary Intake – A high intake of foods rich in choline (e.g., eggs, liver) and carnitine (e.g., red meat) can increase TMA production

2. Gut Microbiota Composition – The relative abundance of TMA-producing bacteria in the gut microbiota varies among individuals and can be influenced by diet, antibiotics, probiotics and overall gut health

Managing TMA Production

The management of TMA production to reduce the symptoms of conditions like trimethylaminuria (TMAU) is possible via

• Dietary Adjustments – Reducing the intake of foods high in choline and carnitine can help lower TMA production

• Probiotics and Prebiotics – Modulating the gut microbiota through probiotics and prebiotics may help reduce the population of TMA-producing bacteria

Conclusion

Several gut bacteria, including those from the Enterobacteriaceae, Clostridiaceae, Desulfovibrionaceae, Ruminococcaceae and Bacteroidaceae families are involved in the production of TMA from dietary choline, carnitine,and betaine.

Understanding the role of these bacteria, and managing their activity through dietary and microbiota-targeted strategies, can help control TMA production and mitigate symptoms of TMAU and extra-oral halitosis.