Isolation of Helicobacter pylori from sheep-implications for transmission to humans.

OBJECTIVES: When and how Helicobacter pylori (H. pylori) originally entered the human population as well as how the infection is transmitted in different communities is unknown. We previously showed that Sardinian shepherds had almost a 100% prevalence of H. pylori and that the prevalence was higher than that of their same-household siblings. AIM: To examine whether H. pylori infection might be transmitted from sheep. METHODS: Milk and gastric tissue were cultured and analyzed by PCR amplification using three sets of primers Helicobacter genus-specific 16S rRNA and two sets of primers specific for H. pylori vacA gene. RESULTS: Helicobacter DNA was demonstrated in 60% (38/63) of milk samples and in 30% (6/20) of sheep tissue samples. H. pylori vacA gene was amplified in five of 38 milk samples, and in two of six sheep tissue samples respectively. H. pylori were cultured from sheep milk and tissue samples and confirmed as H. pylori on the basis of colony morphology, positive biochemical reactions, and negative Gram stain. Sequence analysis of 16S rRNA PCR products from these isolates demonstrated 99% identity with H. pylori. CONCLUSIONS: Together, the presence of H. pylori in sheep stomach in the absence of associated gastritis and recovery of H. pylori from sheep milk and gastric tissue suggest that sheep may be a natural host for H. pylori.