Oral reservoirs of Helicobacter pylori infection: too much to stomach?

Helicobacter pylori (HP) is a motile bacterium that thrives under the acidic pH conditions found in the human stomach. It was first reported in 1983, when Warren and Marshall showed that gastric ulcers were caused by bacteria - namely HP - and not stress. This organism has been associated with chronic gastritis and peptic ulcer disease as well as with gastric cancer and mucosa-associated lymphoid tissue (MALT) lymphoma. HP has also been implicated in the pathogenesis of halitosis, glossitis and recurrent aphthous stomatitis.

Because it has been detected in saliva and in dental plaque using culture and by molecular methods, the question arises as to whether HP may be transmitted orally between individuals, from oral microflora as its major reservoir. This could occur when mothers taste or premasticate food before feeding infants, or who feed their children using their own chopsticks.

The idea of an oral reservoir of HP has been quite controversial, since it could be argued that finding HP in the mouth could simply reflect intermittent episodes of gastroesophageal reflux. Indeed, HP can occur in the oral cavity aside and independently from the stomach and more than one HP genotype may exist in the same patient.

Nevertheless, there is now an emerging story that HP can be detected fairly consistently in the oral cavity in many individuals, that re-infection of the stomach occurs from re-colonization from dental plaque and that recurrence of HP infection in the stomach is more likely among individuals who harbour HP in their oral cavity. In fact, when HP is present in dental plaque biofilm, it is protected from systemic antibiotics administered for the management of gastric HP infection and thus it can persist in the oral cavity even after successful eradication from the stomach. More HP is found in the mouths of patients with untreated periodontitis. This leads to the exciting notion that dental treatment, in particular periodontal therapy, may have additional benefit for patients who are positive for HP infection and who suffer from dyspepsia, since this would reduce the chance of relapse after antimicrobial therapy for the HP infection.

In December 2019, a Japanese study reported HP in the root canal system of teeth that were cariously involved, indicating that this could be a further protected site of colonization by this important bacterium.

A range of clinical studies have been exploring the benefits of dental treatment to disrupt oral reservoirs of HP infection and in future considering endodontic sites as well as periodontal sites will be worthwhile.

Further reading

1. Anand PS, Kamath KP, Anil S. Role of dental plaque, saliva and periodontal disease in Helicobacter pylori infection. World J Gastroenterol. 2014;20(19):5639-53. doi: 10.3748/wjg.v20.i19.5639.
2. Payão SL, Rasmussen LT. Helicobacter pylori and its reservoirs: A correlation with the gastric infection. World J Gastrointest Pharmacol Ther. 2016;7(1):126-32. doi: 10.4292/wjgpt.v7.i1.126.
3. Iwai K, et al. Association between Helicobacter pylori infection and dental pulp reservoirs in Japanese adults. BMC Oral Health. 2019;19(1):267. doi: 10.1186/s12903-019-0967-2.