Oral Helicobacter pylori: a scoping review and pilot study on the PCR-culture detection paradox

The role of the oral cavity as a reservoir for Helicobacter pylori remains controversial. This hybrid study, combining a scoping review and a pilot clinical study, aimed to synthesise global evidence on oral H. pylori detection and investigate the discrepancy between molecular and culture-based findings.

A scoping review following JBI and PRISMA-ScR guidelines identified human studies reporting oral H. pylori detection using molecular and/or culture-based methods. Review findings guided a pilot clinical study in which supragingival plaque and oral mucosal swabs were collected from symptomatic and asymptomatic H. pylori-positive individuals. Detection was performed using nested PCR (16 S rRNA and ureA) and selective microaerophilic culture.

Thirty-nine studies involving over 3,000 participants were included. Molecular detection rates varied widely (0-90%), while culture-confirmed viable H. pylori was exceedingly rare and restricted to protected anaerobic oral niches. In the pilot study (n = 8), PCR detected H. pylori DNA in 50% of participants, with higher detection in mucosal swabs (37.5%) than supragingival plaque (25%). No viable organisms were recovered by culture, which was dominated by commensal oral species.

Both the scoping review and pilot study consistently demonstrated a PCR-positive/culture-negative pattern for oral H. pylori. These findings suggest that oral detection likely reflects transient bacterial presence rather than stable colonisation. Future studies should employ multi-gene molecular assays, targeted sampling, viability-based techniques, and gastric-oral strain comparisons to clarify the biological significance of oral H. pylori detection.

Although H. pylori DNA is frequently detected in oral samples, viable organisms are rarely identified. Oral PCR positivity should therefore not be interpreted as active infection, and clinical management should continue to rely on established gastric diagnostic pathways.