Helicobacter suis and Helicobacter pylori infection in a colony of research macaques: characterization and clinical correlates

Abstract

Introduction. Helicobacter suis ( Helicobacter heilmannii type 1) commonly infects nonhuman primates but its clinical importance is in question. Aim. To characterize H. suis infection in a colony of rhesus macaques (Macaca mulatta) used in cognitive neuroscience research. Hypothesis/Gap Statement. Inquiries into the nature of Helicobacter suis in nonhuman primates are required to further define the organism’s virulence and the experimental animal’s gastric microbiome. Methodology. Animals with and without clinical signs of vomiting and abdominal pain (n=5 and n=16, respectively) were evaluated by histology, culture, PCR amplification and sequencing, fluorescent in situ hybridization (FISH) and serology. Three of the five animals with clinical signs, an index case and two others, were evaluated before and after antimicrobial therapy. Results. The index animal had endoscopically visible ulcers and multifocal, moderate, chronic lymphoplasmacytic gastritis with intraglandular and luminal spiral bacteria. Antimicrobial therapy in the index animal achieved histologic improvement, elimination of endoscopically visible ulcers, and evident eradication but clinical signs persisted. In the other treated animals, gastritis scores were not consistently altered, gastric bacteria persisted, but vomiting and abdominal discomfort abated. Nineteen of 21 animals were PCR positive for H. suis and five animals were also PCR positive for H. pylori . Organisms were detected by FISH in 17 of 21 animals: 16S rRNA sequences of two of these were shown to be H. suis . Mild to moderate lymphoplasmacytic gastritis was seen in antrum, body and cardia, with antral gastritis more likely to be moderate than that of the body. Conclusion. No clear association between the bacterial numbers of Helicobacter spp. and the degree of inflammation was observed. H. suis is prevalent in this colony of Macaca mulatta but its clinical importance remains unclear. This study corroborates many of the findings in earlier studies of H. suis infection in macaques but also identifies at least one animal in which gastritis and endoscopically visible gastric ulcers were strongly associated with H. suis infection. In this study, serology was an inadequate biomarker for endoscopic evaluation in diagnosis of H. suis infection.