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

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.

The Incidence of Lymphoplasmacytic Gastritis in the Fundus and Antrum of Cynomolgus Monkey ( Macaca fascicularis ) Stomachs

Lymphoplasmacytic gastritis is a concern for toxicological pathologists reading preclinical, non-human primate toxicity studies because subtle gastric changes which could be treatment-related may be masked and gastritis lesions may be confused with treatment-related effects and thus a gastric finding may be incorrectly assigned as a treatment-related lesion. This paper discusses the incidence of lymphoplasmacytic gastritis in cynomolgus monkeys at a contract research organization. The incidence of lymphoplasmacytic gastritis in the fundus and antrum of control cynomolgus monkeys on 18 non-gastric compound studies, was scored. The average fundus score ranged from 0.3 to 1.5 and the average antral score ranged from 0.9 to 3.5 in the cynomolgus monkey stomachs examined. The number of affected control animals in a study ranged from 0 to 5 control animals. No correlation between the route of vehicle administration and the severity or incidence of the lesions was noted. The percentage incidence of affected animals ranged from 0 to 100%. An increased incidence lymphoplasmatic gastritis from 2000 to 2004 was noted. The implications of lymphoplasmacytic gastritis in cynomolgus monkeys used for acute toxicity studies are discussed.

Novel intestinal Helicobacter species isolated from cotton-top tamarins (Saguinus oedipus) with chronic colitis

A disease similar to ulcerative colitis in humans has been identified in cotton-top tamarins (CTTs) in captivity. The clinical signs include weight loss, diarrhea, and rectal bleeding with the pathological features and biochemical abnormalities of ulcerative colitis. Approximately 25 to 40% of these animals develop colon cancer after 2 to 5 years of captivity. An infectious etiology has been proposed; however, no microbial agent to date has been identified. Helicobacter spp. have been associated with enterocolitis and inflammatory bowel disease (IBD) in humans and animals. Infection with Helicobacter pylori or Helicobacter mustelae is associated with an increased risk of gastric adenocarcinoma and lymphoma of the mucosa-associated lymphoid tissue. Helicobacter hepaticus causes hepatitis, hepatic adenomas, and hepatocellular carcinomas in susceptible strains of mice. The aim of this study was to assess a colony of CTTs with a high incidence of IBD and colon cancer for the presence of colonic Helicobacter spp. A fusiform, gram-negative bacterium with bipolar flagella and periplasmic fibers was isolated from the feces of CTTs. The bacterium grew under microaerobic conditions at 37 and 42 degrees C but not at 25 degrees C, did not hydrolyze urea, was positive for catalase and oxidase, did not reduce nitrate to nitrite, did not hydrolyze indoxyl acetate or alkaline phosphatase, and was resistant to nalidixic acid, cephalothin, and trimethoprim-sulfamethoxazole. On the basis of 16S rRNA gene sequence analysis, the organism was classified as a novel Helicobacter species. This is the first Helicobacter isolated from CTTs. Further studies are needed to elucidate the role of this novel Helicobacter sp. in the pathogenesis of ulcerative colitis and colonic adenocarcinoma in CTTs.

An epizootic of lymphoplasmacytic gastritis attributed to Helicobacter pylori infection in cynomolgus monkeys (Macaca fascicularis)

An epizootic of subclinical lymphoplasmacytic gastritis occurred in cynomolgus monkeys maintained at our research facility. Gastric pathology data and histologic sections of 63 adolescent monkeys (2.5-3.5 years old) sacrificed during the epizootic were reviewed. Localized to multifocal reddening of the gastric mucosa was noted grossly in 7 of 44 (16%) monkeys harboring Helicobacter pylori, but not in any of 19 monkeys in which these bacteria were not seen. Gastritis, characterized by accentuation of lymphoplasmacytic infiltrates in antral and to a lesser degree cardiac mucosa, occurred in 42 of 63 (67%) monkeys evaluated and in 42 of 44 (93%) monkeys in which H. pylori was observed microscopically. Two monkeys with H. pylori infection had infiltrate scores that overlapped with the upper limit of scores of H. pylori-negative animals. Coincident with accentuated infiltrates were gastric gland epithelial hyperplasia, reduction in mucin content of surface and gland epithelia, and comparatively minor infiltrates of neutrophils in superficial lamina propria and gastric glands. Antral mucosa thickness often exceeded 1.5 to 2 times normal. Antral mucosal erosions occurred in 7 of 44 (16%) monkeys with H. pylori. Argyrophilic bacteria morphologically consistent with H. pylori were present in antral and less commonly cardiac mucosal glands. Intensity of bacterial colonization correlated with lymphoplasmacytic infiltrates (r = 0.754) and hyperplasia (r = 0.700), although responses were quite variable. These bacteria were not detected in fundic mucosa except in instances where parietal cells were substantially depleted in glands coincident with localized increases in lamina propria inflammatory cell infiltrates. Helicobacter heilmannii-like organisms (HHLOs) were present in fundic glands of all 63 monkeys; colonization was often pronounced. Scores for fundic mucosal inflammation did not correlate with presence or intensity of colonization with HHLOs (r = 0.005). Rather, fundic inflammation scores positively correlated with the antral inflammation scores (r = 0.548). Bacteria morphologically, biochemically, and genetically consistent with H. pylori were cultured from gastric mucosal specimens confirming bacterial identification. These findings demonstrate that adolescent cynomolgus monkeys are susceptible to natural infection with H. pylori and develop many morphologic hallmarks of H. pylori-related gastritis in humans.

Helicobacter-like organisms: histopathological examination of gastric biopsies from dogs and cats

Gastric biopsies from the fundic gland region of 122 dogs and 127 cats were subjected to histopathological examination. The aim of the study was to determine infection rates and degrees of colonization by Helicobacter-like organisms (HLOs), and to ascertain their possible relationship to histopathological changes. In all, 82% of the dogs and 76% of the cats had an HLO infection. The most striking histopathological changes were glandular degeneration with accumulation of lymphocytes and neutrophilic granulocytes (dogs, 21%; cats, 39%), fibrosis of the lamina propria mucosae (dogs, 41%; cats, 58%), oedema in the lamina propria mucosae (dogs, 54%; cats, 23%), lymphoid follicles (dogs, 17%; cats, 19%) and lymphoplasmacytic infiltrates. A relation between the degree of colonization by HLOs and the extent of histopathological changes could only be discovered in the cats. It was not possible to ascertain whether these bacteria, irrespective of the degree of colonization, were responsible for the histopathological changes in the dogs.

Gastric injury and invasion of parietal cells by spiral bacteria in rhesus monkeys. Are gastritis and hyperchlorhydria infectious diseases?

The possibility of using the rhesus monkey as a model for studying gastric function in the presence of infection with spiral bacteria was studied. Endoscopic evaluation of the gastric mucosa was performed under general anesthesia in 29 colony-bred rhesus monkeys, and gastric pinch biopsy specimens were obtained from each animal. On a separate day, gastric emptying and acid output were determined using a 99mTc dilution technique. Biopsy samples were fixed for light microscopy (H&E, Gram, and Warthin-Starry stains) and for transmission electron microscopy. The presence of spiral bacteria and gastritis was assessed and rated on coded slides. In 8 of 29 monkeys, Helicobacter pylori-like organisms were observed in close proximity to the mucosal epithelial cells or in the lumen of the gastric pits. In 14 other monkeys, "Gastrospirillum hominis"-like organisms were observed in the mucus covering the surface of epithelial cells, in the lumina of the gastric glands, and overlying parietal cells. Gastritis was present in 8 of 8 animals positive for H. pylori-like organisms, in 2 of 14 animals positive for "G. hominis"-like organisms, and in none of the uninfected monkeys, and the mean gastritis index was significantly greater in animals positive for H. pylori-like organisms. Moreover, acid output was significantly higher in monkeys positive for "G. hominis"-like organisms than in controls or animals positive for H. pylori-like organisms. Gastric emptying was not significantly different in the three groups. In conclusion, (a) H. pylori-like, but not "G. hominis"-like, organisms cause gastritis while not modifying acid output; (b) "G. hominis"-like, but not H. pylori-like organisms, invade and on occasion damage parietal cells while apparently causing hyperchlorhydria; and (c) the rhesus monkey appears to be a good model for the study of gastric infection with spiral bacteria.

A spiral microorganism in the stomach of pigs

Light and electron microscopic and microbiologic evaluations were performed on mucosa of stomachs from 120 healthy slaughtered pigs. Helicobacter pylori was not found, but a tightly spiralled bacterium, not previously described, was seen in histological sections and/or in carbol fuchsin stained smears in 13 (10.8%) stomachs. In paraffin sections stained with carbol fuchsin, the bacteria were seen in the mucus of the lumen of the antral pits and in the mucosa surface within and beneath the mucus. In this sections of Polilyte embedded tissue the bacteria had three to eight spiral turns per cell (mean = five), flattened ends, a Gram-negative cell-wall structure and a sheathed flagella. The urease test was positive in gastric mucosa of 13 bacteria-positive pigs (10.8%). The microorganism was not cultured and did not cross-react with polyclonal antibodies raised in rabbits against H. pylori. Superficial chronic gastritis and "borderline" gastritis were observed in antral mucosa of 10 (76.9%) and of two (15.4%) spiral bacteria-positive pigs, respectively.