Cultivation and molecular characterization of viable Helicobacter pylori from the root canal of 170 deciduous teeth of children

Abstract

Background Helicobacter pylori is a persistent pathogen in the human stomach. However, the proposed transmission route via the oral cavity is not understood and under intense debate. While dozens of studies have shown by PCR that H. pylori DNA is frequently present in the oral cavity, data on the growth and characterization of viable H. pylori from this compartment are very scarce, and it is unclear whether the bacteria can survive in the oral cavity for longer time periods or even colonize it. Methods Selective growth methods, scanning electron microscopy, urease assay, Western blotting, PCR, and gene sequencing were applied to identify and examine viable H. pylori in decayed milk teeth. Results Here, we studied viable H. pylori in the plaque and root canals of 170 endodontically infected deciduous teeth that were extracted from 54 children. While H. pylori DNA was detected in several plaque and many root canal samples by PCR, live bacteria could only be cultivated from 28 root canals, but not from plaque. These 28 isolates have been identified as H. pylori by PCR and sequencing of vacA, cagA and htrA genes, phylogenetic analyses, protein expression of major H. pylori virulence factors, and by signal transduction events during infection of human cell lines. Conclusions Thus, the microaerobic environment in the root canals of endodontically infected teeth may represent a protected and transient reservoir for live H. pylori, especially in individuals with poor dental hygiene, which could serve as a potential source for re-infection of the stomach after antibiotic therapy or for transmission to other individuals.