Helicobacter species infect the gastrointestinal tracts of many animals from birds through humans. Some of these have been linked to a range of human diseases including chronic gastritis, peptic ulcer disease, mucosa-associated lymphoid tissue lymphoma, and gastric adenocarcinoma. The principal Helicobacter infection in humans is Helicobacter pylori, with infection rates in developing countries reaching 50 percent to 90 percent. Human gastric biopsy samples, however, have shown to harbour bacteria which were morphologically different from H pylori. These include Helicobacter heilmannii and Helicobacter felis which are primarily pathogens of domestic animals and were later found to infect humans as well. Gastric non-Helicobacter pylori helicobacters constitute a diverse group of bacterial species that are known to colonise the gastric mucosa of several animals. These include morphologically distinct, typically long spiral shaped bacteria originally referred to as Gastrospirillum hominis and later as H heilmannii. The latter was further subdivided in two taxa: types 1 and 2. H heilmannii type 1 are identical to H suis which colonises the stomachs of pigs. The former H heilmannii type 2 represent a group of species, known to colonise the gastric mucosa of dogs and cats and include H felis, H bizzozeronii, H salomonis, H cynogastricus, H baculiformis and a bacterium provisionally named in 2004 as ‘Candidatus H heilmannii’ because at that time, it could not be cultured in vitro. However, recently, in vitro cultures have been obtained resulting in description of H heilmannii, as a novel Helicobacter species. Sequencing of the 16S or 23S rRNA-encoding genes allows differentiation of H suis from the other gastric non-H pylori helicobacters species, but it cannot distinguish between H felis, H bizzozeronii, H salomonis, H cynogastricus, H baculiformis and Candidatus H heilmannii. For differentiation between these species, sequencing of the heat shock protein 60 or gyrase B gene is used, while sequencing of the urease A and B genes is considered to be the most suitable method since sequences of these genes are available. Dyspepsia describes a variety of symptoms, including abdominal pain, bloating, nausea, and vomiting. In these patients, endoscopy is considered to rule out gastroesophageal reflux disease, peptic or duodenal ulcer and gastric cancer. The role of H pylori infection in dyspepsia remains controversial. This study aims to identify the prevalence of H pylori and non-H pylori helicobacters, H felis and H heilmannii and to analyse the gastric pathology associated with coinfection of these organisms in patients presenting with dyspepsia.
STUDY POPULATION: Between September 2009 and February 2011, a total of 250 patients with abdominal pain or discomfort who attended the gastroenterology outpatient clinic at a tertiary care hospital in Karachi were enrolled. The mean age of these patients was 39 ± 12 years, (range 18-75) with males 162 (65 percent) and females 88 (35 percent). Of these, 136 (54 percent) were in the age group of 18-39 years, 88 (35 percent) in the group of 40-55 years and 26 (10 percent) in the group of 56-75 years. Ethical approval for the study was obtained from the Aga Khan University Ethics Review Committee. Informed consent was taken for participation in the study. A complete socio-demographic questionnaire including determination of socio-economic status, educational level, ownership of the place of residence, number of rooms in the house, number of people living in the household beside siblings, source of water supply, for example, municipal water pipeline or bore water (ground water) and type of latrine in use, was obtained from the patients. A history of exposure of enrolled patients to cats and dogs was determined and a physical examination was carried out. Inclusion criteria were ambulatory adult males and non-pregnant females; age 18 years or older; and patients with upper GI symptoms including abdominal/epigastric pain or discomfort, postprandial abdominal distension, postprandial nausea and vomiting. Exclusion criteria included receiving treatment for H pylori, concurrent or recent antibiotic use such as metronidazole, clarithromycin, amoxicillin, tetracycline, doxycycline and other cephalosporin; histamine-2 receptor blocker or proton pump inhibitor therapy and bismuth compounds in the last four weeks; patients with regular use of NSAID; patients with severe concomitant disease; and patients with upper GI surgery. A crowding index with three categories was constructed by dividing the number of individuals per household by the number of the rooms used as bedrooms. A participant’s household crowding was defined as ‘low’ if they scored an index of 0-1, ‘moderately-crowded’ were 2-4 and > 4 were ‘highly crowded’. On EGD, 242 (97 percent) were found to have endoscopic gastritis alone, while 8 (3 percent) had duodenal ulcer. Biopsy specimens from the gastric corpus and antrum were taken for rapid urease test (RUT) or histopathology for the diagnosis of H pylori and DNA extraction for polymerase chain reaction (PCR) to amplify H pylori, H felis and H heilmannii genes. Ninety patients (36 percent) out of 250 had a RUT done, while 160 (64 percent) out of 250 had histology and provided gastric biopsy specimen for the detection of Helicobacter species.
RESULTS AND DISCUSSION: Majority of the patients with H pylori infection were in the age range of 18-39 years, while H felis and H heilmannii positive patients did not show this distribution. There was no difference in the gender, ethnicity of patients, crowding index (CI) and source of water distribution among the patients with H pylori and non-H pylori infections. All patients had abdominal pain with endoscopic gastritis as the predominant finding. The false positive and false negative results obtained with RUT were 15 (36 percent) and 6 (12 percent), respectively, while with histology the false positive and false negative results obtained were 20 (30 percent) and 10 (11 percent), respectively. Univariate analysis was performed by using the independent sample t-test, Pearson’s chi-squared test or Fisher’s exact test where appropriate. A p-value of < 0.05 was considered as statistically significant. All the H heilmannii and H felis PCR positive patients were also positive for H pylori PCR amplification. PCR for Helicobacter genus specific 16S rDNA was positive in 167/250 (67 percent), glmM (H pylori) in 142/250 (57 percent), H heilmannii in 17/250 (6 percent) and H felis in 10/250 (4 percent), respectively. PCR was positive for both H pylori and H heilmannii in 17 (6 percent) and for H pylori and H felis in 10 (4 percent), respectively. All the H heilmannii and H felis positive patients were also positive for H pylori glmM PCR amplification. Twenty-six percent (66 out of 250) were exposed to pets, either cats or dogs. Most H heilmannii positive patients did not have pet contact. Only one out of 66 exposed to pets was positive for H heilmannii and two for H felis. A higher degree of bacterial density was associated with H pylori infection alone (p < 0.001). Chronic active inflammation was observed in 53 (56 percent) cases with H pylori alone infection (p = 0.001) compared to 3 (37 percent) in H heilmannii (p = 0.73) and 3 (60 percent) in H felis positive patients coinfected with H pylori (p = 0.66). Intestinal metaplasia (IM) was present in 3 (3 percent) out of 94 cases with H pylori infection alone compared to 2 (25 percent) out of 8 cases of H Heilmannii and H pylori coinfection, and 1 (20 percent) out of 5 cases of H felis and H pylori coinfection in which histology has been performed. PCR product sequences were compared to the sequences of urease B of different H heilmannii and H felis strains. The H heilmannii sequences had 100 percent similarity to ‘Candidatus Helicobacter heilmannii’ strains GenBank: AF508012 and L25079, while it was 99 percent to GenBank: AY139170, AF507996, AY139172, AY139173, and 98 percent to GenBank: AY139171, respectively. The H felis sequences had 100 percent similarity to H felis strains GenBank: FQ670179 and X69080, while it was 99 percent to H felis GenBank: AY368267, AY368261, and 98 percent to GenBank: DQ865138, respectively. Among our patients, the cohort exposed to pet animals was limited to 26 percent. There were more patients with H pylori infection who were in the 18-39 years age range. Such age distribution was not seen in cases with H felis and H heilmannii infection. There was no difference in the gender, ethnicity of patients, CI and source of water distribution among the patients with H pylori and non-H pylori helicobacter species infections. There were no statistically significant differences in the endoscopic findings in patients with H pylori infection alone or with coinfection of H pylori and non-H pylori Helicobacter species. Chronic active inflammation was associated with H pylori infection compared to H heilmannii or H felis coinfections with H pylori. However, the histology was not obtained in all the cases that showed H heilmannii and H felis infection. Intestinal metaplasia was present in 2 (25 percent) out of 8 cases of H heilmannii coinfection with H pylori and in 1 (20 percent) out of 5 cases of H felis coinfection with H pylori as compared to 3 (3 percent) of 94 cases with H pylori infection alone who had undergone the histological study. Although it was not possible to draw a conclusion that IM was significantly associated with the coinfection of either of the species and H pylori, a tendency in that way would be likely, as it has also been reported by other authors. PCR positives at the species level were also positive for the Helicobacter genus specific 16S rDNA and all the H heilmannii and H felis positive patients were also positive for H pylori glmM PCR. PCR product sequences of urease B gene of H heilmannii had shown 100 percent similarity to Candidatus H heilmannii strains GenBank: AF508012 and L25079, while H felis sequences had shown 100 percent similarity to strains GenBank: FQ670179 and X69080. In this study, we used urease gene-based PCR method that detected only Candidatus H heilmannii DNA from pure in vitro cultures of other non-H pylori helicobacter species. This method was also used by other investigators to demonstrate the presence of Candidatus H heilmannii DNA in gastric biopsies from patients with dyspepsia. The limitations of our study include the small number of patients who had non-H pylori helicobacter infection and the presence of H pylori co-infection which precluded assessment of the histological effect of these species under consideration. Also, the significance of coinfection in terms of disease development could not be determined. We could have identified few more cases of non-H pylori helicobacter species by other reported methods used to study non-H pylori helicobacter species including fluorescent in situ hybridisation, transmission electron microscopy and partial 16S ribosomal sequencing for analyses of the amplified products. The implications of this study are that non-H pylori helicobacter species infection occurs in patients with abdominal pain or discomfort similar to H pylori infection. Most of our H heilmannii infections were not associated with contact with animals. This is in contrast to a previous analysis of 125 patients with confirmed H heilmannii infection that showed some 70.3 percent of the 111 patients had a history of contact with one or more animals. All of our patients with non-H pylori infection had endoscopic gastritis, though their association with peptic ulcer is well known. The prevalence of coinfection of H felis with H pylori in our population is less than what has been reported from South Africa among African population but is certainly higher than that for H heilmannii and H pylori from the northern Europe which showed that only 1.6 percent had concomitant infection with H pylori. The coinfection in our patients demonstrated severe gastric pathology, as intestinal metaplasia was present in 25 percent of H heilmannii coinfection with H pylori, while in 20 percent of H felis coinfection with H pylori. This was also reported in previous studies. In this study, the difference was not statistically significant due to the number of subjects in each group. The routine transmission of H pylori appears to be human-human whereas non-H pylori helicobacter species are transmitted by cats, dogs, etc. Consequently, the prevalence of H heilmannii is expected to be significantly higher in environment with less hygiene and higher physical exposure to animals. However, in our study there was a negative association with pet contact as the patients reported limited exposure to these animals. There is a need to look into other modes of transmission of these infections.
CONCLUSION: As non-H pylori Helicobacter species are capable of producing complications similar to H pylori so the identification of these species may be of importance in patients with dyspepsia. However, our study fails to show any increased risk of infection with these organisms on exposure to pet animals and any additional complications associated with coinfection in patients infected with H pylori.
Extracted from ‘Prevalence of non-Helicobacter pylori species in patients presenting with dyspepsia’ authored by Javed Yakoob, Zaigham Abbas, Rustam Khan, Shagufta Naz, Zubair Ahmad, Muhammad Islam, Safia Awan, Fatima Jafri and Wasim Jafri.
