Development of a noninvasive method for detecting and monitoring the time course of Helicobacter pylori infection

Protocol to establish an accelerated murine model for Helicobacter-induced gastric cancer

Helicobacter-induced gastric cancer progresses very slowly, even in animal models, making it difficult to study. Here, we present a protocol to establish an accelerated murine model for Helicobacter-induced gastric cancer. We describe steps for infecting mice with Helicobacter felis, harvesting gastric tissue, assessing disease severity by histopathologic scoring, and performing gene expression studies with RT-qPCR and RNA sequencing. The accelerated model shows rapid progression of the disease, with gastric precancerous lesions developing within 6 months post-infection with Helicobacter. For complete details on the use and execution of this protocol, please refer to Bali et al.1.

Detection of Helicobacter felis in a cat with gastric disease in laboratory animal facility

A 3-month-old male cat in the animal facility was presented for investigation of anorexia and occasional vomiting. We collected the specimens from gastroscopic biopsy and stool collection. The gastroscopic biopsy specimens were tested using a rapid urease test, CLO Helicobacter-detection kits. Stool specimens were gathered and evaluated using the commercially available SD Bioline H. pylori Ag kit according to the manufacturer's instructions. Genomic DNAs from gastroscopic biopsy and stool specimens of the cat were extracted and submitted to the consensus PCR to amplify Helicobacter rpoB gene. Then the DNAs from gastroscopic biopsy and stool specimens were conducted a multiplex species-specific PCR to amplify urease B gene for H. heilmannii, H. pylori and H. felis. As the results, the rapid urease test with gastroscopic biopsy was revealed positive reaction. The result of H. pylori Stool Ag assay was one red line, negative for H. pylori. The gastroscopic biopsy and stool specimen were positive reactions by the consensus PCR reaction using the RNA polymerase beta-subunit-coding gene (rpoB) to detect Helicobacter species. By multiplex species-specific PCR with gastroscopic biopsy and stool specimens, no amplification products corresponding to either H. heilmannii or H. pylori were detected, but the specimens tested were positive for H. felis. This case was confirmed as gastroenteric disease induced by H. felis infection. On our knowledge, this is a very rare report about H. felis-induced gastroenteric disease in cat and may provide a valuable data on the study of feline Helicobacter infection.

Comparison of three diagnostic assays for the identification of Helicobacter spp. in laboratory dogs

A number of Helicobacter species may confound experimental data because of their association with disease progressing in various kinds of laboratory animals. Screening of Helicobacter species is particularly desirable, because they are prevalent in commercial and research animal facilities. The aim of the present study was to compare three diagnostic methods [e.g. Helicobacter stool antigen kit (HpSA), polymerase chain reaction (PCR) and rapid urease test (RUT)] for the identification of Helicobacter spp. in stools or gastric biopsy specimens collected from eight dogs suffering from gastritis. The gastroscopic biopsy specimens were tested using RUT and PCR, while stool specimens were evaluated using both HpSA and PCR. DNAs from the gastric biopsies and stool specimens were analyzed by both a consensus PCR that amplified the RNA polymerase beta-subunit-coding gene (rpoB) of Helicobacter spp. and a species-specific PCR to amplify the urease B gene of Helicobacter heilmannii, Helicobacter pylori, and Helicobacter felis. Helicobacter spp. were detected in 62.5% of the dogs, while H. heilmannii and H. felis were identified in 37.5 and 25% of the dogs, respectively. The HpSA did not efficiently detect Helicobacter spp. in the stool samples compared to the RUT and PCR assays, both of which successfully detected Helicobacter spp. in the two sample types. Finally, we recommend that consensus PCR with stool specimens could be used before the species-specific PCR for identifying Helicobacter species in laboratory dogs.

Usefulness of a Helicobacter pylori stool antigen test for diagnosing H. pylori infected C57BL/6 mice

Among several diagnostic tests, a Helicobacter pylori stool antigen (HpSA) test may offer a useful noninvasive method for diagnosing infection without sacrificing animals. In this study, male C57BL/6 mice (n=6) were infected with H. pylori ATCC 49503 (1×10(8) CFU/mouse) by intragastric inoculation three times at 2-day intervals, and H. pylori infected stool specimens were collected 1, 3, 5, 7, 14, 21 days after infection to assess reliability of the HpSA test. Five of six specimens were positive at 5-21 days after infection, and the sensitivity of the HpSA test was 83.33%. The presence of H. pylori infection was confirmed by the rapid urease test and genomic DNA polymerase chain reaction (PCR), and showed the same results as the HpSA. However, the rapid urease test and genomic DNA PCR are invasive tests and require animal sacrifice to detect H. pylori in gastric biopsy samples. We suggest that an HpSA test kit would be useful and effective for monitoring H. pylori in various laboratory animals, as H. pylori can be easily monitored without sacrificing animals.

Screening Helicobacter pylori genes induced during infection of mouse stomachs

AIM: To investigate the effect of in vivo environment on gene expression in Helicobacter pylori (H. pylori) as it relates to its survival in the host.

METHODS: In vivo expression technology (IVET) systems are used to identify microbial virulence genes. We modified the IVET-transcriptional fusion vector, pIVET8, which uses antibiotic resistance as the basis for selection of candidate genes in host tissues to develop two unique IVET-promoter-screening vectors, pIVET11 and pIVET12. Our novel IVET systems were developed by the fusion of random Sau3A DNA fragments of H. pylori and a tandem-reporter system of chloramphenicol acetyltransferase and beta-galactosidase. Additionally, each vector contains a kanamycin resistance gene. We used a mouse macrophage cell line, RAW 264.7 and mice, as selective media to identify specific genes that H. pylori expresses in vivo. Gene expression studies were conducted by infecting RAW 264.7 cells with H. pylori. This was followed by real time polymerase chain reaction (PCR) analysis to determine the relative expression levels of in vivo induced genes.

RESULTS: In this study, we have identified 31 in vivo induced (ivi) genes in the initial screens. These 31 genes belong to several functional gene families, including several well-known virulence factors that are expressed by the bacterium in infected mouse stomachs. Virulence factors, vacA and cagA, were found in this screen and are known to play important roles in H. pylori infection, colonization and pathogenesis. Their detection validates the efficacy of these screening systems. Some of the identified ivi genes have already been implicated to play an important role in the pathogenesis of H. pylori and other bacterial pathogens such as Escherichia coli and Vibrio cholerae. Transcription profiles of all ivi genes were confirmed by real time PCR analysis of H. pylori RNA isolated from H. pylori infected RAW 264.7 macrophages. We compared the expression profile of H. pylori and RAW 264.7 coculture with that of H. pylori only. Some genes such as cagA, vacA, lpxC, murI, tlpC, trxB, sodB, tnpB, pgi, rbfA and infB showed a 2-20 fold upregulation. Statistically significant upregulation was obtained for all the above mentioned genes (P < 0.05). tlpC, cagA, vacA, sodB, rbfA, infB, tnpB, lpxC and murI were also significantly upregulated (P < 0.01). These data suggest a strong correlation between results obtained in vitro in the macrophage cell line and in the intact animal.

CONCLUSION: The positive identification of these genes demonstrates that our IVET systems are powerful tools for studying H. pylori gene expression in the host environment.

Role of 13C-urea breath test in experimental model of Helicobacter pylori infection in mice

BACKGROUND

Animal models have been widely used to study Helicobacter pylori infection. Evaluation of H. pylori infection status following experimental inoculation of mice usually requires euthanasia. The (13) C-urea breath test ((13) C-UBT) is both sensitive and specific for detection of H. pylori in humans. Thus, it would be very useful to have such a test with the same accuracy for the follow-up of this infection in animal models of gastric infection. Accordingly, the purpose of this study was to develop and evaluate a (13) C-UBT method for following the course of H. pylori infection in a mouse model.

MATERIAL AND METHODS

A total of 50 female C57BL/6 mice were gavaged three times with either 10(8) colony-forming units of H. pylori (n=29) or saline solution only (n=21). After 2 months of infection, mice were fasted for 14 hours and (13) C-UBT was performed using 300 μg of (13) C-urea. The mice were killed, and the stomach was removed and processed for immunohistochemistry and PCR.

RESULTS

The optimal time for breath sample collection in mice was found to be 15 minutes. The (13) C-UBT cutoff was set at 3.0‰ δPDB. Using PCR as the gold standard, the sensitivity of (13) C-UBT and immunohistochemistry was 96.6 and 72.4%, respectively, while the specificity was 85.7 and 95.2%, respectively.

CONCLUSIONS

(13) C-UBT was shown to be a reliable method for the detection of H. pylori infection in C57BL/6 mice and was even more accurate than immunohistochemistry. The use of (13) C-UBT in the mouse model of H. pylori infection can be very useful to detect the bacterium without the need to kill the animals in long-term time course studies.

Olfactomedin 4 down-regulates innate immunity against Helicobacter pylori infection

Olfactomedin 4 (OLFM4) is a glycoprotein that has been found to be up-regulated in inflammatory bowel diseases and Helicobacter pylori infected patients. However, its role in biological processes such as inflammation or other immune response is not known. In this study, we generated OLFM4 KO mice to investigate potential role(s) of OLFM4 in gastric mucosal responses to H. pylori infection. H. pylori colonization in the gastric mucosa of OLFM4 KO mice was significantly lower compared with WT littermates. The reduced bacterial load was associated with enhanced infiltration of inflammatory cells in gastric mucosa. Production and expression of proinflammatory cytokines/chemokines such as IL-1beta, IL-5, IL-12 p70, and MIP-1alpha was increased in OLFM4 KO mice compared with infected controls. Furthermore, we found that OLFM4 is a target gene of NF--kappaB pathway and has a negative feedback effect on NF-kappaB activation induced by H. pylori infection through a direct association with nucleotide oligomerization domain-1 (NOD1) and -2 (NOD2). Together these observations indicate that OLFM4 exerts considerable influence on the host defense against H. pylori infection acting through NOD1 and NOD2 mediated NF-kappaB activation and subsequent cytokines and chemokines production, which in turn inhibit host immune response and contribute to persistence of H. pylori colonization.

Relationship between the β-galactosidase activity in saliva and parameters associated with oral malodor

Volatile sulfur compounds (VSCs) are produced by enzymes capable of transforming S-amino acids to corresponding sulfides. Protein degradation by periodontopathogens plays an important role in this process, and the proteolysis of glycoproteins depends on the initial removal of the carbohydrate side chains. In the present report, we tested the relationship between the β-galactosidase activity in saliva and parameters that influence oral malodor, including daily habits and oral conditions. The prevalence of periodontopathic bacteria was also examined. Forty-nine saliva samples were collected from halitosis patients. Patients were examined for breath odor and other associated parameters. Their breath odor was assessed using an organoleptic test, a portable sulfide monitor and gas chromatography. The presence of periodontopathic bacteria in the saliva was also examined. β-galactosidase activity was measured with the chromogenic substrates 5-bromo-4-chloro-3-indoyl-β-d-galactopyranoside and isopropyl-β-d-thiogalactopyranoside. β-galactosidase activity was positively correlated with malodor strength (organoleptic score, portable sulfide monitor score and VSC concentrations). Enzyme activity was also correlated with the degree of observable tongue coating. However, it showed no relationship with periodontal condition, saliva flow, tooth decay, unfitted restorations or the color of any tongue coating. While there was no relationship with Porphyromonas gingivalis and Treponema denticola, there was a negative correlation with Prevotella intermedia. These results indicate that β-galactosidase activity plays an important role in malodor production. Interestingly, the activity of this enzyme was not related to the presence of periodontopathic bacteria, which are the main malodor-producing organisms. The results obtained here may have been associated with physiologic halitosis, which is not necessarily associated with oral problems or with periodontopathic bacteria.

Detection of Helicobacter pylori DNA in the saliva of patients complaining of halitosis

Helicobacter pylori infection, which causes peptic ulcers and gastric cancer, is considered a possible cause of halitosis. Recently, the oral cavity was identified as a possible H. pylori reservoir, particularly in the presence of periodontal disease, which is a cause of halitosis. The purpose of this study was to evaluate by PCR the prevalence of oral H. pylori in the saliva of subjects complaining of halitosis. Samples were obtained from 326 non-dyspeptic subjects, comprising 251 subjects with actual malodour and 75 subjects without halitosis. DNA was extracted from the samples, and the presence of H. pylori and periodontopathic bacteria including Porphyromonas gingivalis, Treponema denticola and Prevotella intermedia was examined by PCR. H. pylori was detected in 21 (6.4 %) of 326 samples. The methyl mercaptan concentration and periodontal parameters including tooth mobility, periodontal pocket depth (PPD) and occult blood in the saliva were significantly greater in the H. pylori-positive subjects. Each of the periodontopathic bacteria was also detected at a significantly higher frequency in the H. pylori-positive subjects. Among those patients with a PPD of > or =5 mm and a tongue coating score of < or =2, no difference was observed in oral malodour levels between the H. pylori-positive and -negative subjects. However, the presence of occult blood in the saliva and the prevalence of Prevotella intermedia were significantly greater in the H. pylori-positive subjects. H. pylori was detected in 16 (15.7 %) of 102 subjects with periodontitis, suggesting that progression of periodontal pocket and inflammation may favour colonization by this species and that H. pylori infection may be indirectly associated with oral pathological halitosis following periodontitis.

Regulation of cell growth during serum starvation and bacterial survival in macrophages by the bifunctional enzyme SpoT in Helicobacter pylori

In Helicobacter pylori the stringent response is mediated solely by spoT. The spoT gene is known to encode (p)ppGpp synthetase activity and is required for H. pylori survival in the stationary phase. However, neither the hydrolase activity of the H. pylori SpoT protein nor the role of SpoT in the regulation of growth during serum starvation and intracellular survival of H. pylori in macrophages has been determined. In this study, we examined the effects of SpoT on these factors. Our results showed that the H. pylori spoT gene encodes a bifunctional enzyme with both a hydrolase activity and the previously described (p)ppGpp synthetase activity, as determined by introducing the gene into Escherichia coli relA and spoT defective strains. Also, we found that SpoT mediates a serum starvation response, which not only restricts the growth but also maintains the helical morphology of H. pylori. Strikingly, a spoT null mutant was able to grow to a higher density in serum-free medium than the wild-type strain, mimicking the "relaxed" growth phenotype of an E. coli relA mutant during amino acid starvation. Finally, SpoT was found to be important for intracellular survival in macrophages during phagocytosis. The unique role of (p)ppGpp in cell growth during serum starvation, in the stress response, and in the persistence of H. pylori is discussed.