Correlative Light and Electron Microscopy Visualization of Helicobacter pylori in Human Saliva

Helicobacter pylori is a Class I carcinogen that primarily colonizes the gastric mucosa. However, its presence in the oral cavity remains poorly characterized, particularly at the ultrastructural level. Saliva represents a practical, noninvasive oral specimen, yet previous reports have relied on indirect detection methods with limited morphological confirmation. In this study, we aimed to visualize H. pylori in human saliva using correlative light and electron microscopy (CLEM). Unstimulated saliva samples were collected from 36 patients and immunostained with a monoclonal anti-H. pylori antibody. Fluorescence-positive regions identified by confocal microscopy were examined by field emission scanning electron microscopy (FE-SEM). Gastric H. pylori infection status was determined by Giemsa staining of biopsy specimens. H. pylori-positive signals were detected in 63.9% of total saliva samples, with similar detection rates in gastric infection-positive (62.5%) and gastric infection-negative (65.0%) groups. Notably, unlike gastric forms, salivary H. pylori exhibited exclusively coccoid or intermediate forms, with no spiral shapes observed. To our knowledge, this study provides the first CLEM-based ultrastructural visualization of H. pylori in human saliva. These findings indicate that such structures can be detected regardless of gastric infection status and demonstrate morphological diversity that may reflect adaptation to the oral environment.