Direct DNA fingerprinting of Helicobacter pylori in dental plaque by PCR amplification and restriction analysis of urease a gene sequences

Abstract

The human mouth may act as a reservoir for Helicobacter pylori infection. A novel DNA-based fingerprinting technique was developed to compare dental plaque extracts with gastric biopsy cultures for evidence of common strain types at the two sites within an individual. Diversity within a 200 bp region of the ureA gene from six unrelated strains was demonstrated by DNA sequencing with up to seven single base substitutions detected. The 361 bp ureA nested polymerase chain reaction (PCR) amplicons from DNA derived from dental plaque extracts and gastric cultures were compared by Mboll restriction endonuclease analysis. Restriction length polymorphisms (RFLPs) were evident within the ureA segment and three distinct fingerprints of three or four bands were found. Results of a comparison between samples from oral and gastric sites demonstrated matching H. pylori strain types in two individuals, whereas six other individuals had different strain types. The results indicated the PCR restriction endonuclease analysis method can be applied directly to dental plaque without the need for positive culture of H. pylori. It is a rapid method and has potential for monitoring persistent H. pylori reinfection and for studies on its transmission within families.