Persistent hepatitis and enterocolitis in germfree mice infected with Helicobacter hepaticus

Practice guidelines for the management of Helicobacter pylori infection: The Saudi H. pylori Working Group recommendations

The eradication rates for Helicobacter pylori globally are decreasing with a dramatic increase in the prevalence of antibiotic resistant bacteria all over the world, including Saudi Arabia. There is no current consensus on the management of H. pylori in Saudi Arabia. The Saudi Gastroenterology Association developed these practice guidelines after reviewing the local and regional studies on the management of H. pylori. The aim was to establish recommendations to guide healthcare providers in managing H. pylori in Saudi Arabia. Experts in the areas of H. pylori management and microbiology were invited to write these guidelines. A literature search was performed, and all authors participated in writing and reviewing the guidelines. In addition, international guidelines and consensus reports were reviewed to bridge the gap in knowledge when local and regional data were unavailable. There is limited local data on treatment of H. pylori. The rate of clarithromycin and metronidazole resistance is high; therefore, standard triple therapy for 10-14 days is no longer recommended in the treatment of H. pylori unless antimicrobial susceptibility testing was performed. Based on the available data, bismuth quadruple therapy for 10-14 days is considered the best first-line and second-line therapy. Culture and antimicrobial susceptibility testing should be considered following two treatment failures. These recommendations are intended to provide the most relevant evidence-based guidelines for the management of H. pylori infection in Saudi Arabia. The working group recommends further studies to explore more therapeutic options to eradicate H. pylori.

Validation of Multiplex PCR and Serology Detecting Helicobacter Species in Mice

High-throughput multiplexed assays are needed to simplify detection of Helicobacter species in experimental infection and routine health monitoring of laboratory mice. Therefore, fluorescent bead-based hybridization assays for Helicobacter sp. DNA and serology were developed. Multiplex PCR amplicons (H. hepaticus, H. bilis, H. typhlonius, H. pylori, H. muridarum, H. pullorum, H. cinaedi, H. heilmanii, C. jejuni) and antibodies against H. pylori, H. hepaticus, H. bilis were assessed in naturally and experimentally infected mice, and results compared to conventional PCR. Species-specific and sensitive detection of seven Helicobacter spp. <100 copies/PCR, and of two species <1000 copies/PCR was successfully established in the Helicobacter multiplex DNA finder. The novel assay was highly comparable with conventional PCR (kappa = 0.98, 95%CI: 0.94-1.00). Antibody detection of H. hepaticus and H. bilis showed low sensitivity (71% and 62%, respectively) and cross-reactivity in H. typhlonius-infected mice. Infection experiments showed that antibodies develop earliest two weeks after DNA detection in feces. In conclusion, detection of Helicobacter antibodies showed low sensitivity depending on the timing relative to infection. However, Helicobacter multiplex DNA finder is a sensitive and specific high-throughput assay applicable in routine health monitoring for laboratory animals.

Enterohepatic Helicobacter species - clinical importance, host range, and zoonotic potential

The genus Helicobacter defined just over 30 years ago, is a highly diverse and fast-growing group of bacteria that are able to persistently colonize a wide range of animals. The members of this genus are subdivided into two groups with different ecological niches, associated pathologies, and phylogenetic relationships: the gastric Helicobacter (GH) and the enterohepatic Helicobacter (EHH) species. Although GH have been mostly studied, EHH species have become increasingly important as emerging human pathogens and potential zoonotic agents in the last years. This group of bacteria has been associated with the development of several diseases in humans from acute pathologies like gastroenteritis to chronic pathologies that include inflammatory bowel disease, and liver and gallbladder diseases. However, their reservoirs, as well as their routes of transmission, have not been well established yet. Therefore, this review summarizes the current knowledge of taxonomy, epidemiology, and clinical role of the EHH group.

Seropositivity for Helicobacter pylori and hepatobiliary cancers in the PLCO study

Helicobacter has been suggested to play a possible role in hepatitis, gallstones, and hepatobiliary tumours. We assessed whether seropositivity to 15 H. pylori proteins was associated with subsequent incidence of 74 biliary tract and 105 liver cancer cases vs. 357 matched controls in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO). Odds ratios and 95% confidence intervals were computed by conditional logistic regression after adjustment for known hepatobiliary cancer risk factors. H. pylori seropositivity was not associated with either biliary tract (1.76, 0.90–3.46) or liver cancer (0.87, 0.46–1.65). CagA seropositivity was associated with both endpoints, although the latter association was not statistically significant (biliary tract: 2.16, 1.03–4.50; liver cancer: 1.96, 0.98–3.93) and neither association was statistically significant after correcting for multiple comparisons. Together, these results suggest possible associations between H. pylori and hepatobiliary cancer and suggest the value of future studies investigating the association.

Trial registration number: NCT00339495.

Helicobacter infection in the hepatobiliary system and hepatic lesions: a possible association in dogs

Helicobacter infection has been associated with hepatobiliary diseases in humans and animals. The aims of this study were to identify Helicobacter species in the hepatobiliary tract of dogs and to elucidate the possible association of these bacteria in liver diseases. Twenty-seven gastric and hepatobiliary samples were collected from 33 dogs with hepatic lesions and 17 dogs with no liver histological changes. Warthin-Starry staining, immunohistochemical assay, and PCR were performed to detect the presence of Helicobacter. Helicobacter genus was detected in 21.2% of the samples with hepatic lesions. The main lesion was chronic hepatitis. Immunohistochemistry revealed infection in liver (1/5) and gallbladder (1/3) 32 samples. The sequence analysis of seven amplicons of the 16S rRNA gene of Helicobacter genus from hepatobiliary samples showed 97.8 to 100% of nucleotide identity with gastric helicobacter. One amplicon of the ureA and ureB gene of Helicobacter genus from the stomach showed 89.1 to 90.7% nucleotide identity with H. heilmannii. The presence of Helicobacter genus in liver samples showing hepatic lesions suggests the involvement of these bacteria in the etiology of hepatobiliary disease in dogs. DNA sequences were similar to gastric Helicobacter species, reinforcing the hypothesis of bacterial translocation from the stomach to liver by the biliary pathway.

Helicobacter pylori Infection as a Risk Factor for Hepatocellular Carcinoma: A Case-Control Study in Ethiopia

Background and Aims. Hepatocellular carcinoma is a major cause of cancer death worldwide, accounting for over half a million deaths per year. Its incidence varies with geographic locations and the type of etiologic factors. In Ethiopia, unidentified causes of liver disease are of sizeable proportion. Recent studies have shown an association of H. pylori infection with different spectrums of chronic liver disease. This study was conducted at St. Paul's Hospital Millennium Medical College in Ethiopia and assesses liver cancer and the association with H. pylori infection. Method. A prospective case-control study conducted on patients with chronic liver disease presenting with a suspicious liver lesion and diagnosed to have HCC in the Gastrointestinal (GI) Clinic of St. Paul's Hospital MMC from Dec 30, 2016, to Nov 1, 2017 G.C. Descriptive surveys on clinical history and physical examination and laboratory profiles were obtained, and the clinical course of the patients including the type of treatment was followed prospectively. Control cases were taken from adult patients without evidence of liver disease in the internal medicine clinic coming for routine evaluation. After collection data were analyzed using SPSS version 23 and associations were assessed using chi-square test. Binary logistic regression was used to assess the association of HCC with different variables and H. pylori infection. All variables with p-value <0.05 were considered as statistically significant. Results. One hundred twenty patients were analyzed with equal representation of cases and controls. The majority of patients with HCC were male with a mean age of 36 years. Older age adjusted Odds Ratio (AOR) (95%CI, p-value) 1.07(1.03-1.09, <0.001), viral hepatitis B (AOR) (95%CI, p-value) 6.19 (1.92-19.93, 0.002), and H. pylori infection (AOR) (95%CI, p-value) 5.22 (2.04-13.31, <0.001) were statistically significantly associated with HCC. Conclusion. H. pylori infection is associated with HCC in this case-control study. This study supports the emerging evidence of H. pylori association with other extra-gastric manifestations.

Gamma-glutamyltranspeptidase expression by Helicobacter saguini, an enterohepatic Helicobacter species isolated from cotton top tamarins with chronic colitis

BACKGROUND

Helicobacter saguini is a novel enterohepatic Helicobacter species isolated from captive cotton top tamarins with chronic colitis and colon cancer. Monoassociated H. saguini infection in gnotobiotic IL-10^-/- mice causes typhlocolitis and dysplasia; however, the virulent mechanisms of this species are unknown. Gamma-glutamyltranspeptidase (GGT) is an enzymatic virulence factor expressed by pathogenic Helicobacter and Campylobacter species that inhibits host cellular proliferation and promotes inflammatory-mediated gastrointestinal pathology. The aim of this study was to determine if H. saguini expresses an enzymatically active GGT homologue with virulence properties.

EXPERIMENTAL PROCEDURES

Two putative GGT paralogs (HSGGT1 and HSGGT2) identified in the H. saguini genome were bioinformatically analysed to predict enzymatic functionality and virulence potential. An isogenic knockout mutant strain and purified recombinant protein of HSGGT1 were created to study enzymatic activity and virulence properties by in vitro biochemical and cell culture experiments.

RESULTS

Bioinformatic analysis predicted that HSGGT1 has enzymatic functionality and is most similar to the virulent homologue expressed by Helicobacter bilis, whereas HSGGT2 contains putatively inactivating mutations. An isogenic knockout mutant strain and recombinant HSGGT1 protein were successfully created and demonstrated that H. saguini has GGT enzymatic activity. Recombinant HSGGT1 protein and sonicate from wild-type but not mutant H. saguini inhibited gastrointestinal epithelial and lymphocyte cell proliferation without evidence of cell death. The antiproliferative effect by H. saguini sonicate or recombinant HSGGT1 protein could be significantly prevented with glutamine supplementation or the GGT-selective inhibitor acivicin. Recombinant HSGGT1 protein also induced proinflammatory gene expression in colon epithelial cells.

CONCLUSIONS

This study shows that H. saguini may express GGT as a potential virulence factor and supports further in vitro and in vitro studies into how GGT expression by enterohepatic Helicobacter species influences the pathogenesis of gastrointestinal inflammatory diseases.

Male Syrian Hamsters Experimentally Infected with Helicobacter spp. of the H. bilis Cluster Develop MALT-Associated Gastrointestinal Lymphomas

BACKGROUND

Aged hamsters naturally infected with novel Helicobacter spp. classified in the H. bilis cluster develop hepatobiliary lesions and typhlocolitis.

METHODS

To determine whether enterohepatic H. spp. contribute to disease, Helicobacter-free hamsters were experimentally infected with H. spp. after suppression of intestinal bacteria by tetracycline treatment of dams and pups. After antibiotic withdrawal, weanlings were gavaged with four H. bilis-like Helicobacter spp. isolated from hamsters or H. bilis ATCC 43879 isolated from human feces and compared to controls (n = 7 per group).

RESULTS

Helicobacter bilis 43879-dosed hamsters were necropsied at 33 weeks postinfection (WPI) due to the lack of detectable infection by fecal PCR; at necropsy, 5 of 7 were weakly PCR positive but lacked intestinal lesions. The remaining hamsters were maintained for ~95 WPI; chronic H. spp. infection in hamsters (6/7) was confirmed by PCR, bacterial culture, fluorescent in situ hybridization, and ELISA. Hamsters had mild-to-moderate typhlitis, and three of the male H. spp.-infected hamsters developed small intestinal lymphoma, in contrast to one control. Of the three lymphomas in H. spp.-infected hamsters, one was a focal ileal mucosa-associated lymphoid tissue (MALT) B-cell lymphoma, while the other two were multicentric small intestinal large B-cell lymphomas involving both the MALT and extra-MALT mucosal sites with lymphoepithelial lesions. The lymphoma in the control hamster was a diffuse small intestinal lymphoma with a mixed population of T and B cells.

CONCLUSIONS

Results suggest persistent H. spp. infection may augment risk for gastrointestinal MALT origin lymphomas. This model is consistent with H. pylori/heilmannii-associated MALT lymphoma in humans and could be further utilized to investigate the mechanisms of intestinal lymphoma development.

Helicobacter cinaedi induced typhlocolitis in Rag-2-deficient mice

BACKGROUND

Helicobacter cinaedi, an enterohepatic helicobacter species (EHS), is an important human pathogen and is associated with a wide range of diseases, especially in immunocompromised patients. It has been convincingly demonstrated that innate immune response to certain pathogenic enteric bacteria is sufficient to initiate colitis and colon carcinogenesis in recombinase-activating gene (Rag)-2-deficient mice model. To better understand the mechanisms of human IBD and its association with development of colon cancer, we investigated whether H. cinaedi could induce pathological changes noted with murine enterohepatic helicobacter infections in the Rag2(-/-) mouse model.

MATERIALS AND METHODS

Sixty 129SvEv Rag2(-/-) mice mouse were experimentally or sham infected orally with H. cinaedi strain CCUG 18818. Gastrointestinal pathology and immune responses in infected and control mice were analyzed at 3, 6 and 9 months postinfection (MPI). H. cinaedi colonized the cecum, colon, and stomach in infected mice.

RESULTS

H. cinaedi induced typhlocolitis in Rag2(-/-) mice by 3 MPI and intestinal lesions became more severe by 9 MPI. H. cinaedi was also associated with the elevation of proinflammatory cytokines, interferon-γ, tumor-necrosis factor-α, IL-1β, IL-10; iNOS mRNA levels were also upregulated in the cecum of infected mice. However, changes in IL-4, IL-6, Cox-2, and c-myc mRNA expressions were not detected.

CONCLUSIONS

Our results indicated that the Rag2(-/-) mouse model will be useful to continue investigating the pathogenicity of H. cinaedi, and to study the association of host immune responses in IBD caused by EHS.

Pathogenicity of Helicobacter ganmani in mice susceptible and resistant to infection with H. hepaticus

Helicobacter spp. are some of the most prevalent bacterial contaminants of laboratory mice. Although abundant data regarding the diseases associated with H. hepaticus infection are available, little is known about the pathogenicity of H. ganmani, which was first isolated in 2001 from the intestines of laboratory mice. The objective of this study was to evaluate the host response to H. ganmani colonization in H. hepaticus disease-resistant C57BL/6 and disease-susceptible A/J and IL10-deficient mice. Mice were inoculated with H. ganmani, H. hepaticus, or Brucella broth. Cecal lesion scores, cecal gene expression, and Helicobacter load were measured at 4 and 90 d after inoculation. At both time points, mice inoculated with H. ganmani had similar or significantly more copies of cecum-associated Helicobacter DNA than did mice inoculated with H. hepaticus. When compared with those of sham-inoculated control mice, cecal lesion scores at 4 and 90 d after inoculation were not significantly greater in H. ganmani-inoculated A/J, C57BL/6, or IL10-deficient mice. Analysis of cecal gene expression demonstrated that H. ganmani infection failed to cause significant elevations of IFNγ in A/J, C57BL/6, or IL10-deficient mice. However, in IL10-deficient mice, H. ganmani infection was associated with a significant increase in the expression of the proinflammatory cytokine IL12/23p40. Although H. ganmani infection in this study failed to induce the typhlitis that is the hallmark of H. hepaticus infection, infection with H. ganmani was associated with alterations in inflammatory cytokines in IL10-deficient mice.

Biology and Diseases of Mice

Today’s laboratory mouse, Mus musculus, has its origins as the ‘house mouse’ of North America and Europe. Beginning with mice bred by mouse fanciers, laboratory stocks (outbred) derived from M. musculus musculus from eastern Europe and M. m. domesticus from western Europe were developed into inbred strains. Since the mid-1980s, additional strains have been developed from Asian mice (M. m. castaneus from Thailand and M. m. molossinus from Japan) and from M. spretus which originated from the western Mediterranean region.

Association of seropositivity to Helicobacter species and biliary tract cancer in the ATBC study

Helicobacter have been detected in human bile and hepatobiliary tissue. Despite evidence that Helicobacter species promote gallstone formation and hepatobiliary tumors in laboratory studies, it remains unclear whether Helicobacter species contribute to these cancers in humans. We used a multiplex panel to assess whether seropositivity to 15 Helicobacter pylori proteins was associated with subsequent incidence of hepatobiliary cancers in the Finnish Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study. We included 64 biliary cancers, 122 liver cancers, and 224 age-matched controls which occurred over the course of 22 years. Helicobacter pylori seropositivity was defined as those positive to ≥ 4 antigens. Odds ratios (OR) and 95% confidence intervals were adjusted for major hepatobiliary cancer risk factors. Among the controls, 88% were seropositive to H. pylori at baseline. Among those who subsequently developed hepatobiliary cancer, the prevalence of seropositivity was higher: 100% for gallbladder cancer, 97% of extrahepatic bile duct cancer, 91% of ampula of Vater cancer, 96% of intrahepatic bile duct cancer, and 94% of hepatocellular carcinoma. Although the OR for gallbladder cancer could not be calculated, the OR for the other sites were 7.01 (95% confidence interval [CI]: 0.79-62.33), 2.21 (0.19-25.52), 10.67 (0.76-150.08), and 1.20 (0.42-3.45), respectively, with an OR of 5.47 (95% CI: 1.17-25.65) observed for the biliary tract cancers combined. ORs above 1 were observed for many of the investigated antigens, although most of these associations were not statistically significant.

CONCLUSION

Seropositivity to H. pylori proteins was associated with an increased risk of biliary tract cancers in ATBC. Further studies are needed to confirm our findings and to determine how H. pylori might influence the risk of biliary tract cancer.

Prevalence of helicobacter in laboratory mice in Thailand

Prevalence of Helicobacter is mostly unknown in laboratory animals in Thailand. The 221 mice feces/cecum from 8 universities, 2 pharmaceutical companies and 3 research institutions in Thailand were surveyed for the prevalence and distribution of Helicobacter species by using the Electrochemical DNA chip. Helicobacter were detected 23/46 samples in Specific Pathogen Free (SPF) and 168/175 in conventional condition. Prevalence of Helicobacter were 98%, 96%, 92% and 78% in South (n=40), Northeast (n=40), North (n=25) and Central area (n=116), respectively. Only Central area holds SPF facility resulting in Helicobacter prevalence that seems to be lower than other areas. Three species of Helicobacter were detected in feces/cecum samples by sequence analysis: H. rodentium (67.0%, 148 samples), Helicobacter sp. MIT 01-6451 (15.4%, 34 samples), and unidentified Helicobacter species (14.1%, 9 samples). The results suggested that H. rodentium is the most common species of Helicobacter in laboratory mice in Thailand.

Helicobacter hepaticus infection promotes hepatitis and preneoplastic foci in farnesoid X receptor (FXR) deficient mice

Farnesoid X receptor (FXR) is a nuclear receptor that regulates bile acid metabolism and transport. Mice lacking expression of FXR (FXR KO) have a high incidence of foci of cellular alterations (FCA) and liver tumors. Here, we report that Helicobacter hepaticus infection is necessary for the development of increased hepatitis scores and FCA in previously Helicobacter-free FXR KO mice. FXR KO and wild-type (WT) mice were sham-treated or orally inoculated with H. hepaticus. At 12 months post-infection, mice were euthanized and liver pathology, gene expression, and the cecal microbiome were analyzed. H. hepaticus induced significant increases hepatitis scores and FCA numbers in FXR KO mice (P<0.01 and P<0.05, respectively). H. hepaticus altered the beta diversity of cecal microbiome in both WT and FXR KO mice compared to uninfected mice (P<0.05). Significant upregulation of β-catenin, Rela, Slc10a1, Tlr2, Nos2, Vdr, and Cyp3a11 was observed in all FXR KO mice compared to controls (P<0.05). Importantly, H. hepaticus and FXR deficiency were necessary to significantly upregulate Cyp2b10 (P<0.01). FXR deficiency was also a potent modulator of the cecal microbiota, as observed by a strong decrease in alpha diversity. A significant decrease in Firmicutes, particularly members of the order Clostridiales, was observed in FXR KO mice (P<0.05 and FDR<5%, ANOVA). While FXR deficiency strongly affects expression of genes related to immunity and bile acid metabolism, as well as the composition of the microbiome; however, its deficiency was not able to produce significant histopathological changes in the absence of H. hepaticus infection.

Effects of medicated diet to eradicate Helicobacter spp. on growth, pathology, and infection status in Rag1-/- and nude mice

The use of a commercial 4-drug diet has been shown to eradicate Helicobacter spp. from immunocompetent mice and those with innate immunodeficiencies. However the efficacy of this diet has not been confirmed in mice with altered adaptive immunity. We hypothesized that an 8-wk treatment with medicated diet would eradicate H. hepaticus and H. typhlonius from young naturally infected nude and Rag1 mice lacking functional T cells (Foxn1(nu)) or T and B cells (B6.129S7-Rag1(tm1Mom)/J), respectively. We evaluated helicobacter status, body weight, and gross and histologic changes between medicated and control diet in groups of infected and uninfected mice throughout treatment and at 8 wk after treatment completion. Initial infection status was confirmed by fecal PCR at weaning and 3 wk later, with study initiation in 7-wk-old mice. PCR testing demonstrated that independent of strain and sex, all treated mice tested negative for Helicobacter spp. after 4 wk of treatment and remained negative for the duration of the study. Irrespective of infection status, nude and Rag1 mice fed 8 wk of medicated diet gained less weight than did their untreated controls. Both strains normalized body weight while on control diet for the 8 wk after treatment. Mice fed medicated diet developed severe gastroesophageal hyperkeratosis, suggestive of reduced feed consumption, and enlarged ceca. These conditions improved or resolved after the return to control diet. This report is the first to demonstrate the efficacy and physical effects of providing medicated diet for the eradication of Helicobacter spp. from mice with adaptive immune deficiencies.

Pathogenic properties of enterohepatic Helicobacter spp. isolated from rhesus macaques with intestinal adenocarcinoma

Considerable progress has been made in understanding the roles of Helicobacter pylori in inflammation and gastric cancer; however, far less is known about the roles of enterohepatic Helicobacter species (EHS) in carcinogenesis and their zoonotic or pathogenic potential. We determined the prevalence of EHS infection in a cohort of geriatric rhesus monkeys in which intestinal adenocarcinoma (IAC) is common and investigated the association between EHS infection and IAC. The cohort consisted of 36 animals, 14 of which (age 26-35 years) had IAC. Of the 36 rhesus, 35 (97%) were positive for EHS using PCR or bacterial isolation from faeces, colonic or tumour tissues. Only a single rhesus, which had IAC, was negative for EHS by all detection methods. The EHS identified by 16S rRNA sequencing in this study were from three Helicobacter taxa: Helicobacter macacae (previously rhesus monkey taxon 1), Helicobacter sp. rhesus monkey taxon 2, previously described from strain MIT 99-5507, and Helicobacter sp. rhesus monkey taxon 4, related to Helicobacter fennelliae. Thirteen of 14 monkeys with IAC were positive for either H. macacae (7/13, 54%), EHS rhesus monkey taxon 4 (4/13, 31%) or a mixture of the two EHS (2/13, 15%). These results indicate that EHS are prevalent among aged rhesus macaques with IAC. Using Helicobacter genus-specific florescent in situ hybridization, EHS were detected on the surface of colonic epithelia of infected monkeys. All Helicobacter isolates, including H. macacae, effectively adhered to, invaded, and significantly induced proinflammatory genes, including IL-8, IL-6, TNF-α and iNOS, while downregulating genes involved in the function of inflammasomes, particularly IL-1β, CASPASE-1, NRLP3, NLRP6 and NLRC4 in the human colonic T84 cell line (P<0.0001). These results suggest that EHS may represent an aetiological agent mediating diarrhoea, chronic inflammation, and possibly intestinal cancer in non-human primates, and may play a role in similar disease syndromes in humans. Downregulation of inflammasome function may represent an EHS strategy for long-term persistence in the host and play a role in inducing pathological changes in the host's lower bowel.

Helicobacter canis colonization in sheep: a Zoonotic link

BACKGROUND

Helicobacter canis has been associated with hepatobiliary and gastrointestinal disease in dogs, cats, and humans. Infection has not been documented in other species.

MATERIALS AND METHODS

Sheep feces subjected to microaerobic culture. Isolates were characterized by genus-specific PCR, restriction fragment length polymorphism, biochemical profiling, and 16S rRNA sequence analysis.

RESULTS

Helicobacter canis was isolated from sheep feces and confirmed by the above methods. These isolates are distinct from other sheep-origin enterohepatic Helicobacter species previously isolated.

CONCLUSIONS

This study identifies sheep as H. canis reservoirs potentially important in zoonotic or foodborne transmission.

Intestinal microbiota composition of interleukin-10 deficient C57BL/6J mice and susceptibility to Helicobacter hepaticus-induced colitis

The mouse pathobiont Helicobacter hepaticus can induce typhlocolitis in interleukin-10-deficient mice, and H. hepaticus infection of immunodeficient mice is widely used as a model to study the role of pathogens and commensal bacteria in the pathogenesis of inflammatory bowel disease. C57BL/6J Il10^−/− mice kept under specific pathogen-free conditions in two different facilities (MHH and MIT), displayed strong differences with respect to their susceptibilities to H. hepaticus-induced intestinal pathology. Mice at MIT developed robust typhlocolitis after infection with H. hepaticus, while mice at MHH developed no significant pathology after infection with the same H. hepaticus strain. We hypothesized that the intestinal microbiota might be responsible for these differences and therefore performed high resolution analysis of the intestinal microbiota composition in uninfected mice from the two facilities by deep sequencing of partial 16S rRNA amplicons. The microbiota composition differed markedly between mice from both facilities. Significant differences were also detected between two groups of MHH mice born in different years. Of the 119 operational taxonomic units (OTUs) that occurred in at least half the cecum or colon samples of at least one mouse group, 24 were only found in MIT mice, and another 13 OTUs could only be found in MHH samples. While most of the MHH-specific OTUs could only be identified to class or family level, the MIT-specific set contained OTUs identified to genus or species level, including the opportunistic pathogen, Bilophila wadsworthia. The susceptibility to H. hepaticus-induced colitis differed considerably between Il10^−/− mice originating from the two institutions. This was associated with significant differences in microbiota composition, highlighting the importance of characterizing the intestinal microbiome when studying murine models of IBD.

Prevalence of murine Helicobacter spp. Infection is reduced by restocking research colonies with Helicobacter-free mice

Most academic research colonies of mice are endemically infected with enterohepatic Helicobacter spp. (EHS). We evaluated EHS prevalence in surveillance mice before and after a 10-y period of requiring that imported mice be free of EHS by embryo transfer rederivation or purchase from approved vendors. In 2009, composite fecal samples from CD1 surveillance mice representing colony health in 57 rooms located in 6 facilities were evaluated for EHS infection by using PCR assays. Fecal samples were screened with primers designed to detect all known EHS, and positive samples were further assayed by using primers specific for H. hepaticus, H. bilis, H. rodentium, and H. typhlonicus. Most EHS were detected in surveillance mice within the first month of dirty bedding exposure, with prevalence ranging from 0% to 64% as monoinfections or, more commonly, infections with multiple EHS. Compared with 1999 prevalence data, EHS remained endemic in colonies importing the lowest number of EHS-free mice. EHS were absent or the prevalence was greatly reduced in colonies receiving the highest percentage of EHS-free mice. This study demonstrates that the management decision to require exclusive importation of EHS-free mice reduced EHS prevalence on an institutional scale without intensive labor and expense associated with other techniques or interference with research objectives.

Natural and experimental Helicobacter pullorum infection in Brown Norway rats

Helicobacter pullorum is an enterohepatic Helicobacter species (EHS) that was recently reported as a naturally acquired infection in mice. Faecal samples from 18 out of 20 Brown Norway (BN) rats, housed in the same barrier as the H. pullorum-infected mice, were positive for H. pullorum using species-specific PCR. In addition, we determined whether H. pullorum was able to persistently colonize the gastrointestinal tract and/or biliary tree and elicit tissue inflammation as well as a serum IgG response in BN rats. Six (four male, two female) 6-week-old, H. pullorum-negative BN rats were orally dosed with 4×10(8) c.f.u. of H. pullorum every other day for a total of three doses. At 2 weeks post-infection, all rats were H. pullorum-positive by faecal PCR. Five out of the six BN rats remained H. pullorum-positive for the entire 30 week study. PCR analysis of tissue collected at necropsy confirmed that the colon and caecum were the primary sites of H. pullorum colonization. Rats that were persistently colonized by H. pullorum had a sustained H. pullorum-specific IgG response measured by ELISA. Intestinal or hepatic pathology associated with H. pullorum infection was not noted. To our knowledge, this is the first report documenting that rats can be persistently colonized with an EHS that also infects humans.

Increased presence of effector lymphocytes during Helicobacter hepaticus-induced colitis

AIM: To identify and characterize drosophila mothers against decapentaplegic (SMAD)3-dependent changes in immune cell populations following infection with Helicobacter hepaticus (H. hepaticus).

METHODS: SMAD3^-/- (n = 19) and colitis-resistant SMAD3^+/- (n = 24) mice (8-10 wk of age) were infected with H. hepaticus and changes in immune cell populations [T lymphocytes, natural killer (NK) cells, T regulatory cells] were measured in the spleen and mesenteric lymph nodes (MsLNs) at 0 d, 3 d, 7 d and 28 d post-infection using flow cytometry. Genotype-dependent changes in T lymphocytes and granzyme B⁺ cells were also assessed after 28 d in proximal colon tissue using immunohistochemistry.

RESULTS: As previously observed, SMAD3^-/-, but not SMAD3^+/- mice, developed colitis, peaking at 4 wk post-infection. No significant changes in T cell subsets were observed in the spleen or in the MsLNs between genotypes at any time point. However, CD4⁺ and CD8⁺/CD62L^lo cells, an effector T lymphocyte population, as well as NK cells (NKp46/DX5⁺) were significantly higher in the MsLNs of SMAD3^-/- mice at 7 d and 28 d post-infection. In the colon, a higher number of CD3⁺ cells were present in SMAD3^-/- compared to SMAD3^+/– mice at baseline, which did not significantly change during infection. However, the number of granzyme B⁺ cells, a marker of cytolytic lymphocytes, significantly increased in SMAD3^-/- mice 28 d post-infection compared to both SMAD3^+/- mice and to baseline values. This was consistent with more severe colitis development in these animals.

CONCLUSION: Data suggest that defects in SMAD3 signaling increase susceptibility to H. hepaticus-induced colitis through aberrant activation and/or dysregulation of effector lymphocytes.

Immunological variation between inbred laboratory mouse strains: points to consider in phenotyping genetically immunomodified mice

Inbred laboratory mouse strains are highly divergent in their immune response patterns as a result of genetic mutations and polymorphisms. The generation of genetically engineered mice (GEM) has, in the past, used embryonic stem (ES) cells for gene targeting from various 129 substrains followed by backcrossing into more fecund mouse strains. Although common inbred mice are considered "immune competent," many have variations in their immune system-some of which have been described-that may affect the phenotype. Recognition of these immune variations among commonly used inbred mouse strains is essential for the accurate interpretation of expected phenotypes or those that may arise unexpectedly. In GEM developed to study specific components of the immune system, accurate evaluation of immune responses must take into consideration not only the gene of interest but also how the background strain and microbial milieu contribute to the manifestation of findings in these mice. This article discusses points to consider regarding immunological differences between the common inbred laboratory mouse strains, particularly in their use as background strains in GEM.

Quantitative trait loci in a bacterially induced model of inflammatory bowel disease

Inflammatory bowel diseases (IBDs) are complex disorders caused by a combination of environmental, microbial, and genetic factors. Genome-wide association studies in humans have successfully identified multiple genes and loci associated with disease susceptibility, but the mechanisms by which these loci interact with each other and/or with environmental factors (i.e., intestinal microbiota) to cause disease are poorly understood. Helicobacter hepaticus-induced intestinal inflammation in mice is an ideal model system for elucidating the genetic basis of IBD susceptibility in a bacterially induced system, as there are significant differences in H. hepaticus-induced disease susceptibility among inbred mouse strains. Infected A/J mice develop acute overexpression of proinflammatory cytokines followed 2-3 months later by chronic cecal inflammation, whereas infected C57BL/6 mice fail to develop cecal inflammation or increased cytokine expression. The goal of this project was to use quantitative trait locus (QTL) mapping to evaluate genetic factors that contribute to the differential disease susceptibility between these two mouse strains. Using acute cecal IL-12/23p40 expression as a biomarker for disease susceptibility, QTL analysis of H. hepaticus-infected F(2) mice revealed involvement of multiple loci. The loci with the strongest association were located on Chromosome 3 and Chromosome 17, with logarithm of odds (LOD) scores of 6.89 and 3.09, respectively. Cecal expression of IL-12/23p40 in H. hepaticus-infected C57BL/6J-Chr3(A/J)/NaJ chromosome substitution mice had an intermediate phenotype, significantly higher than in resistant C57BL/6 but lower than in susceptible A/J mice, confirming the importance of this locus to the immune response to H. hepaticus infection.

Noninvasive detection of inflammation-associated colon cancer in a mouse model

Helicobacter bilis-infected Smad3(-/-) mice represent an attractive model of inflammation-associated colon cancer. Most infected mice develop mucinous adenocarcinoma (MUC) by 6 weeks post inoculation (PI); however, approximately one third do not progress to MUC. The ability to predict the development of MUC in mice used in therapeutic studies would confer a considerable saving of time and money. In addition, the inadvertent use of mice without MUC may confound therapeutic studies by making treatments seem falsely efficacious. We assessed both magnetic resonance imaging (MRI) and fecal biomarkers in Helicobacter- and sham-inoculated mice as methods of noninvasively detecting MUC before the predicted onset of disease. Non-contrast-enhanced MRI was able to detect lesions in 58% of mice with histologically confirmed MUC; however, serial imaging sessions produced inconsistent results. MRI was also a labor- and time-intensive technique requiring anesthesia. Alternatively, inflammatory biomarkers isolated from feces at early time points were correlated to later histologic lesions. Fecal expression of interleukin 1β, macrophage inflammatory protein 1α, and regulated on activation, normal T-cell expressed, and secreted at 3 weeks PI correlated significantly with lesion severity at 9 weeks PI. For each biomarker, receiver-operator characteristic curves were also generated, and all three biomarkers performed well at 1 to 3 weeks PI, indicating that the development of MUC can be predicted based on the early expression of certain inflammatory mediators in feces.

Helicobacter hepaticus infection in mice: models for understanding lower bowel inflammation and cancer

Pioneering work in the 1990s first linked a novel microaerobic bacterium, Helicobacter hepaticus, with chronic active hepatitis and inflammatory bowel disease in several murine models. Targeted H. hepaticus infection experiments subsequently demonstrated its ability to induce colitis, colorectal cancer, and extraintestinal diseases in a number of mouse strains with defects in immune function and/or regulation. H. hepaticus is now widely utilized as a model system to dissect how intestinal microbiota interact with the host to produce both inflammatory and tolerogenic responses. This model has been used to make important advances in understanding factors that regulate both acquired and innate immune response within the intestine. Further, it has been an effective tool to help define the function of regulatory T cells, including their ability to directly inhibit the innate inflammatory response to gut microbiota. The complete genomic sequence of H. hepaticus has advanced the identification of several virulence factors and aided in the elucidation of H. hepaticus pathogenesis. Delineating targets of H. hepaticus virulence factors could facilitate novel approaches to treating microbially induced lower bowel inflammatory diseases.

Ulcerative typhlocolitis associated with Helicobacter mastomyrinus in telomerase-deficient mice

Telomerase deficiency induces early senescence and defects in proliferating cell populations, but in mice it has not been associated with inflammatory bowel disease. Genetically engineered mice lacking either telomerase reverse transcriptase (TERT) or telomerase RNA were examined for chronic diarrhea and wasting. Affected mice had pasty stools, thickened nondistensible colon walls, and contracted ceca. Histologically, the cecal mucosa was largely replaced by inflammatory infiltrate consisting of plasma cells, neutrophils, lymphocytes, and macrophages with marked widespread fibrosis and ulceration. Remaining epithelium was disorganized and hyperplastic, with multifocal dysplasia. Colonic mucosa was markedly hyperplastic with similar inflammation and epithelial dysplasia. Multifocal adenomatous hyperplasia, but no inflammation, was present in the small intestine. Microaerophilic spiral bacteria with 16S rRNA gene sequences identical to Helicobacter mastomyrinus were isolated from the colon and cecum. Severe granulomatous typhlocolitis without epithelial dysplasia developed in germ-free recombination-activating gene (RAG) knockout (KO) recipients of CD4+ T cells and inoculated with cecal contents from affected TERT KO mice and in specific pathogen-free recipient RAG KO mice and interleukin-10 KO mice inoculated with H mastomyrinus. Typhlocolitis in mice given H mastomyrinus was more severe than in mice given Helicobacter hepaticus. Telomerase-deficient mice are susceptible to helicobacter-associated typhlocolitis. H mastomyrinus causes severe disease in susceptible mouse strains.

Experimental Helicobacter marmotae infection in A/J mice causes enterohepatic disease

Helicobacter marmotae has been identified in the inflamed livers of Eastern woodchucks (Marmota monax) infected with woodchuck hepatitis virus (WHV), as well as from the livers of WHV-negative woodchucks. Because the majority of WHV-positive woodchucks with hepatic tumours were culture or PCR positive for this helicobacter, and WHV-negative woodchucks with H. marmotae had hepatitis, the bacterium may have a role in tumour promotion related to chronic inflammation. In this study, the type strain of H. marmotae was inoculated intraperitoneally into 48 male and female A/J mice, a strain noted to be susceptible to Helicobacter hepaticus-induced liver tumours. Sixteen mice served as mock-dosed controls. At 6, 12 and 18 months post-inoculation (p.i.), there were statistically significant (P<0.05) differences in mean inflammation scores for the caecum and proximal colon between experimentally infected and control mice. Differences in hepatic inflammation were significant (P<0.05) at 6 and 12 months p.i. between the two groups but not at the 18 month time point. Two infected male mice had livers with severe hepatitis, and the liver samples were culture positive for H. marmotae. Serum IgG levels in the mice dosed with H. marmotae were elevated for the duration of the study. These results demonstrate that the woodchuck helicobacter can successfully colonize mice and cause enterohepatic disease. In the future, a mouse-adapted strain of H. marmotae could be selected to maximize colonization and lesion development. Such a woodchuck helicobacter-infected mouse model could be used to dissect potential mechanisms of microbial co-carcinogenesis involved in tumour development in woodchucks with WHV and in humans with hepatitis B virus.

Comparative genomics and proteomics of Helicobacter mustelae, an ulcerogenic and carcinogenic gastric pathogen

Background

Helicobacter mustelae causes gastritis, ulcers and gastric cancer in ferrets and other mustelids. H. mustelae remains the only helicobacter other than H. pylori that causes gastric ulceration and cancer in its natural host. To improve understanding of H. mustelae pathogenesis, and the ulcerogenic and carcinogenic potential of helicobacters in general, we sequenced the H. mustelae genome, and identified 425 expressed proteins in the envelope and cytosolic proteome.

Results

The H. mustelae genome lacks orthologs of major H. pylori virulence factors including CagA, VacA, BabA, SabA and OipA. However, it encodes ten autotransporter surface proteins, seven of which were detected in the expressed proteome, and which, except for the Hsr protein, are of unknown function. There are 26 putative outer membrane proteins in H. mustelae, some of which are most similar to the Hof proteins of H. pylori. Although homologs of putative virulence determinants of H. pylori (NapA, plasminogen adhesin, collagenase) and Campylobacter jejuni (CiaB, Peb4a) are present in the H. mustelae genome, it also includes a distinct complement of virulence-related genes including a haemagglutinin/haemolysin protein, and a glycosyl transferase for producing blood group A/B on its lipopolysaccharide. The most highly expressed 264 proteins in the cytosolic proteome included many corresponding proteins from H. pylori, but the rank profile in H. mustelae was distinctive. Of 27 genes shown to be essential for H. pylori colonization of the gerbil, all but three had orthologs in H. mustelae, identifying a shared set of core proteins for gastric persistence.

Conclusions

The determination of the genome sequence and expressed proteome of the ulcerogenic species H mustelae provides a comparative model for H. pylori to investigate bacterial gastric carcinogenesis in mammals, and to suggest ways whereby cag minus H. pylori strains might cause ulceration and cancer.

The genome sequence was deposited in EMBL/GenBank/DDBJ under accession number FN555004.

Acute in vivo interactions of Helicobacter equorum with its equine host

REASONS FOR PERFORMING STUDY

A novel urease-negative Helicobacter species has been isolated from faecal samples of clinically healthy horses, but no information is available about the main sites of colonisation in the equine gastrointestinal tract nor is the pathogenic potential of this microorganism known. An experimental infection in horses was therefore carried out.

METHODS

Four horses were infected with H. equorum strain CCUG 52199T and subjected to euthanasia at 10 (n = 2) and 30 days (n = 2) post inoculation. A fifth animal was inoculated with phosphate buffered saline and used as control. Gastrointestinal samples were examined histologically and bacteriologically. These samples, as well as faecal material collected at regular intervals, were also subjected to PCR analysis.

RESULTS

All horses remained clinically healthy and no specific macroscopic lesions were identified, nor were there any microscopic changes. H. equorum-DNA was detected in the faeces during the whole experiment in all infected animals but not in the negative control. Sites of colonisation were caecum, colon and rectum.

CONCLUSIONS

H. equorum is able to colonise the equine lower bowel and is excreted in faeces without apparent pathology. No association between the presence of the organism and gastrointestinal disease was demonstrated.

Association between entero-hepatic Helicobacter species and Crohn's disease: a prospective cross-sectional study

BACKGROUND

The pathogenesis of Crohn's disease (CD) involved microbial factors. Some Helicobacter species, the so-called entero-hepatic Helicobacters (EHH), can naturally colonize the intestinal surface and have been detected in humans. Aim To look for an association between CD and the presence of EHH DNA in intestinal biopsies.

METHODS

Two groups of patients were included prospectively in a multicentre cross-sectional study: CD patients with an endoscopic post-operative recurrence within 2 years following a surgical resection and controls screened for colorectal polyps or cancer. Intestinal biopsies were taken for Helicobacter culture and Helicobacter 16S DNA detection. If positive, the EHH species were identified with specific PCRs, sequencing and denaturing gradient gel electrophoresis.

RESULTS

In the 165 included patients (73 CD and 92 controls), Helicobacter cultures were negative. PCR was positive in 44% of CD and 47% of controls. After age-adjustment, CD was significantly associated with EHH in intestinal biopsies (OR = 2.58; 95%CI: 1.04-6.67). All EHH species detected were identified as Helicobacter pullorum and the closely related species Helicobacter canadensis.

CONCLUSION

Crohn's disease is associated with the presence of EHH species DNA in intestinal biopsies after adjustment for age. Whether these species play a role in the pathophysiology of CD remains to be determined.

Cytolethal distending toxin promotes Helicobacter cinaedi-associated typhlocolitis in interleukin-10-deficient mice

Helicobacter cinaedi colonizes a wide host range, including rodents, and may be an emerging zoonotic agent. Colonization parameters, pathology, serology, and inflammatory responses to wild-type H. cinaedi (WT(Hc)) were evaluated in B6.129P2-IL-10(tm1Cgn) (IL-10(-/-)) mice for 36 weeks postinfection (WPI) and in C57BL/6 (B6) mice for 12 WPI. Because cytolethal distending toxin (CDT) may be a virulence factor, IL-10(-/-) mice were also infected with the cdtB(Hc) and cdtB-N(Hc) isogenic mutants and evaluated for 12 WPI. Consistent with other murine enterohepatic helicobacters, WT(Hc) did not cause typhlocolitis in B6 mice, but mild to severe lesions developed at the cecocolic junction in IL-10(-/-) mice, despite similar colonization levels of WT(Hc) in the cecum and colon of both B6 and IL-10(-/-) mice. WT(Hc) and cdtB mutants also colonized IL-10(-/-) mice to a similar extent, but infection with either cdtB mutant resulted in attenuated typhlocolitis and hyperplasia compared to infection with WT(Hc) (P < 0.03), and only WT(Hc) infection caused dysplasia and intramucosal carcinoma. WT(Hc) and cdtB(Hc) mutant infection of IL-10(-/-) mice elevated mRNA expression of tumor necrosis factor alpha, inducible nitric oxide synthase, and gamma interferon in the cecum, as well as elevated Th1-associated serum immunoglobulin G2a(b) compared to infection of B6 mice (P < 0.05). Although no hepatitis was noted, liver samples were PCR positive at various time points for WT(Hc) or the cdtB(Hc) mutant in approximately 33% of IL-10(-/-) mice and in 10 to 20% of WT(Hc)-infected B6 mice. These results indicate that WT(Hc) can be used to model inflammatory bowel disease in IL-10(-/-) mice and that CDT contributes to the virulence of H. cinaedi.

Effects of Helicobacter infection on research: the case for eradication of Helicobacter from rodent research colonies

Infection of mouse colonies with Helicobacter spp. has become an increasing concern for the research community. Although Helicobacter infection may cause clinical disease, investigators may be unaware that their laboratory mice are infected because the pathology of Helicobacter species is host-dependent and may not be recognized clinically. The effects of Helicobacter infections are not limited to the gastrointestinal system and can affect reproduction, the development of cancers in gastrointestinal organs and remote organs such as the breast, responses to vaccines, and other areas of research. The data we present in this review show clearly that unintentional Helicobacter infection has the potential to significantly interfere with the reliability of research studies based on murine models. Therefore, frequent screening of rodent research colonies for Helicobacter spp. and the eradication of these pathogens should be key goals of the research community.

Lurking in the shadows: emerging rodent infectious diseases

Rodent parvoviruses, Helicobacter spp., murine norovirus, and several other previously unknown infectious agents have emerged in laboratory rodents relatively recently. These agents have been discovered serendipitously or through active investigation of atypical serology results, cell culture contamination, unexpected histopathology, or previously unrecognized clinical disease syndromes. The potential research impact of these agents is not fully known. Infected rodents have demonstrated immunomodulation, tumor suppression, clinical disease (particularly in immunodeficient rodents), and histopathology. Perturbations of organismal and cellular physiology also likely occur. These agents posed unique challenges to laboratory animal resource programs once discovered; it was necessary to develop specific diagnostic assays and an understanding of their epidemiology and transmission routes before attempting eradication, and then evaluate eradication methods for efficacy. Even then management approaches varied significantly, from apathy to total exclusion, and such inconsistency has hindered the sharing and transfer of rodents among institutions, particularly for genetically modified rodent models that may not be readily available. As additional infectious agents are discovered in laboratory rodents in coming years, much of what researchers have learned from experiences with the recently identified pathogens will be applicable. This article provides an overview of the discovery, detection, and research impact of infectious agents recently identified in laboratory rodents. We also discuss emerging syndromes for which there is a suspected infectious etiology, and the unique challenges of managing newly emerging infectious agents.

Influence of Helicobacter hepaticus infection on the chronic toxicity and carcinogenicity of triethanolamine in B6C3F1 mice

Helicobacter hepaticus (H. hepaticus) infection causes hepatitis and increased hepatocellular neoplasms in male mice; although females are also infected, liver lesions are not typically expressed. In the 1990s, B6C3F1 mice from some chronic National Toxicology Program (NTP) studies were found to be infected with H. hepaticus. In these studies, there was hepatitis in many of the males, and there were more hepatocellular neoplasms in control males compared to studies with uninfected mice. In one of these studies, increased hepatocellular neoplasms at the high doses in male and female mice exposed topically to triethanolamine (TEA) provided the only evidence of carcinogenic activity. This study was repeated in mice free of H. hepaticus.However, the NTP mouse production colony and the diet differed between studies; these differences were the result of NTP programmatic decisions. In repeat study males, although control incidences were similar between studies, exposure did not result in increased hepatocellular neoplasms. In repeat study females, the control incidence of hepatocellular neoplasms was half that observed in the initial study, and these neoplasms were increased over controls at all doses. These data suggest that in the initial study, H. hepaticusinfluenced the induction of hepatocellular neoplasms in males, but not in females.

Marked liver tumorigenesis by Helicobacter hepaticus requires perinatal exposure

BACKGROUND

Although severe hepatitis and liver tumors occur in a high percentage of A/J male mice naturally infected with Helicobacter hepaticus, these effects have not been observed after injection of adult mice with the bacteria.

OBJECTIVES

We tested the hypothesis that perinatal exposure to the bacteria is required for liver tumorigenesis.

METHODS

A/J female mice were infected by intragastric (ig) or intraperitoneal (ip) treatment with 1.5 x 10(8) H. hepaticus before pregnancy. We examined offspring at progressive time intervals, including some kept until natural death in old age. A/J, BALB/c, and C57BL/6 weanling male mice were similarly treated ig with the bacteria and observed for up to 2 years.

RESULTS

After ip bacterial infection of A/J females, 41% of their male offspring developed hepatitis and 33% had hepatocellular tumors, including 18% with hepatocellular carcinoma. Treatment by the ig route resulted in a similar incidence of hepatitis in offspring (35%) but fewer total liver tumors (8%) and carcinomas (4%). By contrast, ig instillation of H. hepaticus in weanling A/J, C57BL/6, or BALB/c mice resulted in low incidence of hepatitis (0-20%) and few liver tumors, despite presence of bacteria confirmed in feces.

CONCLUSIONS

Results indicate that a high incidence of liver tumors in mice infected with H. hepaticus requires perinatal exposure. Contributing perinatal factors could include known high sensitivity of neonatal liver to tumor initiation, and/or modulation of immune response to the bacterium or its toxins. Mechanisms of human perinatal sensitivity to such phenomena can be studied with this model.

Detection of enterohepatic and gastric helicobacter species in fecal specimens of children with Crohn's disease

BACKGROUND

Although there is compelling evidence to support the role of bacteria in Crohn's disease (CD), there is currently no solid evidence to support the role of any one specific bacterial causative agent. Recent studies have suggested that members of the Helicobacteraceae may play a role in the development of CD. The aim of this study was to further investigate the presence of members of the Helicobacteraceae in children with and without CD.

MATERIALS AND METHODS

Fecal specimens from 29 children with CD, 11 healthy, normal controls, and 26 symptomatic controls with non-inflammatory bowel disease (IBD) pathology were obtained for DNA extraction and subjected to Helicobacteraceae-specific polymerase chain reaction (PCR). All PCR-positive samples were sequenced. The association between the presence of members of the Helicobacteraceae and each study group was statistically analysed using the Fisher's exact test.

RESULTS

Based on Helicobacteraceae-specific PCR analysis, 59% (17 of 29) of the children with CD were positive, which was significantly higher than that in asymptomatic healthy children [9% (1 of 11); p = .01] and that in symptomatic children with non-IBD pathology [0% (0/26); p < .0001]. Sequencing of the 16S rRNA gene of positive samples revealed the presence of both enterohepatic Helicobacter species and Helicobacter pylori in fecal specimens.

CONCLUSIONS

For the first time, enterohepatic and gastric Helicobacter species have been identified in fecal specimens from children diagnosed with CD using PCR. Our data suggest that Helicobacter species may have a pathogenic role in the development of CD in a considerable proportion of children.

Characterization of a Helicobacter hepaticus putA mutant strain in host colonization and oxidative stress

Helicobacter hepaticus is a gram-negative, spiral-shaped microaerophilic bacterium associated with chronic intestinal infection leading to hepatitis and colonic and hepatic carcinomas in susceptible strains of mice. In the closely related human pathogen Helicobacter pylori, L-proline is a preferred respiratory substrate and is found at significantly high levels in the gastric juice of infected patients. A previous study of the proline catabolic PutA flavoenzymes from H. pylori and H. hepaticus revealed that Helicobacter PutA generates reactive oxygen species during proline oxidation by transferring electrons from reduced flavin to molecular oxygen. We further explored the preference for proline as a respiratory substrate and the potential impact of proline metabolism on the redox environment in Helicobacter species during host infection by disrupting the putA gene in H. hepaticus. The resulting putA knockout mutant strain was characterized by oxidative stress analysis and mouse infection studies. The putA mutant strain of H. hepaticus exhibited increased proline levels and resistance to oxidative stress relative to that of the wild-type strain, consistent with proline's role as an antioxidant. The significant increase in stress resistance was attributed to higher proline content, as no upregulation of antioxidant genes was observed for the putA mutant strain. The wild-type and putA mutant H. hepaticus strains displayed similar levels of infection in mice, but in mice challenged with the putA mutant strain, significantly reduced inflammation was observed, suggesting a role for proline metabolism in H. hepaticus pathogenicity in vivo.

Procuration and identification of bacteria in paraffin-embedded liver tissues of hepatocellular carcinoma by laser-assisted microdissection technique

This study was aimed at procuring directly and identifying the bacteria which had been found in paraffin-embedded liver tissues of hepatocellular carcinoma (HCC) patients. In our previous studies, Helicobacter spp. had been detected by polymerase chain reaction (PCR) and observed by histology in the liver tissues of HCC patients but had never been cultured successfully. To obtain and identify the uncultured bacteria, laser microdissection and pressure catapulting (LMPC) techniques were applied. Following microdissection from the liver tissue sections, these bacteria were examined by PCR using Helicobacter genus-specific 16S rRNA primers and sequence analysis. Amplified products of 16S rRNA were positive in all six microdissected samples with bacteria, and showed 99%-100% similarity with Helicobacter pylori by sequence analysis. Another H. pylori-specific 26 kDa gene (encoding one 26 kDa protein as H. pylori-specific antigen) was also tested by PCR. Four of six samples were positive. Therefore, Helicobacter spp. detected by PCR in the liver tissues of HCC patients in our previous studies are actually the bacteria observed by histology and identified as H. pylori by further sequence analysis. The laser-assisted microdissection technique can be extensively applied for identification of bacteria in tissue samples in bacteriology research.

Immunogenicity and pathogenicity of Helicobacter infections of veterinary animals

The initial discovery that the human stomach is commonly infected by the bacterium Helicobacter pylori subsequently resulted in the identification of a whole new family of pathogenic bacteria. In less than 25 years, the Helicobacter genus has grown from obscurity to number at least 38 different species with many more awaiting classifications. These bacteria, many of which are either direct or opportunistic pathogens, are present in virtually every mammalian species examined, and have also now been identified in a number of birds. The pathogenesis associated with these infections is predominantly the result of a chronic inflammatory response mounted by the host against the infection. This is typically a Th1-driven response which can result in a range of conditions from hepatitis, through gallstones to cancer. In some cases the inflammatory response to these infections is normally well managed by the host and disease only results when there is a breakdown or misbalance in the immunoregulatory process, which for example can result in inflammatory bowel disease in experimental models. Understanding the disease association and pathogenic mechanisms of the different Helicobacter infections is clearly of potential significance not only from an animal welfare point of view but also from the growing realisation of how commonly transmission of Helicobacter occurs between different mammals, including pathogenic zoonotic infections of humans.

Enterohepatic Helicobacter species are prevalent in mice from commercial and academic institutions in Asia, Europe, and North America

The discovery of Helicobacter hepaticus and its role in hepatitis, hepatocellular carcinoma, typhlocolitis, and lower-bowel carcinoma in murine colonies was followed by the isolation and characterization of other Helicobacter spp. involved in enterohepatic disease. Colonization of mouse colonies with members of the family Helicobacteriaceae has become an increasing concern for the research community. From 2001 to 2005, shipments of selected gift mice from other institutions and mice received from specified commercial vendors were screened for Helicobacter spp. by culture of cecal tissue. The identities of the isolates were confirmed by genus-specific PCR, followed by species-specific PCR and restriction fragment length polymorphism analysis. Sequencing of the 16S rRNA gene was performed if the species identity was not apparent. The survey included 79 mice from 34 sources: 2 commercial sources and 16 research sources from the United States and 1 commercial source and 15 research sources from Canada, Europe, or Asia. Helicobacter spp. were cultured from the ceca of 62 of 79 mice. No Helicobacter spp. were found in mice from advertised Helicobacter-free production areas from two U.S. vendors. Multiple Helicobacter spp. were found in mice from one vendor's acknowledged Helicobacter-infected production area. The European commercial vendor had mice infected with novel Helicobacter sp. strain MIT 96-1001. Of the U.S. academic institutions, 6 of 16 (37%) had mice infected with Helicobacter hepaticus; but monoinfection with H. bilis, H. mastomyrinus, H. rodentium, and MIT 96-1001 was also encountered, as were mice infected simultaneously with two Helicobacter spp. Non-U.S. academic institutions had mice that were either monoinfected with H. hepaticus, monoinfected with seven other Helicobacter spp., or infected with a combination of Helicobacter spp. This survey indicates that 30 of 34 (88%) commercial and academic institutions in Canada, Europe, Asia, Australia, and the United States have mouse colonies infected with Helicobacter spp. Mice from 20 of the 34 institutions (59%) were most commonly colonized with H. hepaticus alone or in combination with other Helicobacter spp. These results indicate that a broad range of Helicobacter spp. infect mouse research colonies. The potential impact of these organisms on in vivo experiments continues to be an important issue for mice being used for biomedical research.

Helicobacter bilis: bacterial provocateur orchestrates host immune responses to commensal flora in a model of inflammatory bowel disease

Helicobacter bilis can elicit heterologous immune responses to lower gut flora

Helicobacter bilis triggers persistent immune reactivity to antigens derived from the commensal bacteria in gnotobiotic C3H/HeN mice

BACKGROUND

Infection with Helicobacter species has been associated with the development of mucosal inflammation and inflammatory bowel disease (IBD) in several mouse models. However, consensus regarding the role of Helicobacter as a model organism to study microbial-induced IBD is confounded by the presence of a complex colonic microbiota.

AIM

To investigate the kinetics and inflammatory effects of immune system activation to commensal bacteria following H bilis colonisation in gnotobiotic mice.

METHODS

C3H/HeN mice harbouring an altered Schaedler flora (ASF) were selectively colonised with H bilis and host responses were investigated over a 10-week period. Control mice were colonised only with the defined flora (DF). Tissues were analysed for gross/histopathological lesions, and bacterial antigen-specific antibody and T-cell responses.

RESULTS

Gnotobiotic mice colonised with H bilis developed mild macroscopic and microscopic lesions of typhlocolitis beginning 3 weeks postinfection. ASF-specific IgG responses were demonstrable within 3 weeks, persisted throughout the 10-week study, and presented as a mixed IgG1:IgG2a profile. Lymphocytes recovered from the mesenteric lymph node of H bilis-colonised mice produced increased levels of interferon gamma, tumour necrosis factor alpha (TNFalpha), interleukin 6 (IL6) and IL12 in response to stimulation with commensal- or H bilis-specific bacterial lysates. In contrast, DF mice not colonised with H bilis did not develop immune responses to their resident flora and remained disease free.

CONCLUSIONS

Colonisation of gnotobiotic C3H/HeN mice with H bilis perturbs the host's response to its resident flora and induces progressive immune reactivity to commensal bacteria that contributes to the development of immune-mediated intestinal inflammation.