Epidemiology of Helicobacter pylori infection in dyspeptic Ghanaian patients

Introduction Helicobacter pylori is a gram-negative urease-producing bacterium causally linked with gastritis, peptic ulcer disease and gastric adenocarcinoma. Infection is more frequent and acquired at an earlier age in developing countries compared to European populations. The incidence of Helicobacter pylori infection in dyspeptic Ghanaian patients was 75.4%. However, epidemiological factors associated with infection vary across populations. Methods This study used a cross-sectional design to consecutively sample dyspeptic patients at the Endoscopy Unit of the Korle-Bu Teaching Hospital, Accra between 2010 and 2012. The study questionnaire elicited their epidemiological clinical characteristics. Helicobacter pylori infection was confirmed by rapid-urease examination of antral biopsies at upper Gastro-intestinal endoscopy. Results The sample population of dyspeptic patients attending the Endoscopy Unit for upper GI endoscopy yielded 242 patients of which 47.5% were females. The age distribution of H. pylori-infection was even across most age – groups, ranging from 69.2% (61 – 70) years to 80% (21 – 30) years. Helicobacter pylori prevalence decreased across areas mapping to the three residential classes in accordance with increasing affluence with rural areas having the highest prevalence. The unemployed and patients in farming had relatively high Helicobacter pylori infection rates of 92.3% and 91.7% respectively. Conclusion Helicobacter pylori is endemic in Ghana but the persistently high prevalence across age groups despite significant community anti-microbial use suggests likely re-crudescence or re-infection from multiple sources in a developing country. Socio-cultural factors such as residential class and farming may be facilitating factors for its continued prevalence.


Introduction
Helicobacter pylori is a spiral-shaped gram-negative ureaseproducing bacterium [1]. It is the most common chronic bacterial infection known to humans [2,3]. It is found in the gastric antrum and in areas of gastric metaplasia in the duodenum [4]. It has also been established as the main aetiological agent in the development of chronic gastritis, gastric and duodenal ulceration, gastric B-cell lymphoma and distal gastric cancer [4]. H. Pylori has been demonstrated worldwide and in individuals of all ages with conservative estimates suggesting 50 % of the world´s population is affected [3]. Infection is more frequent and acquired at an earlier age in developing countries compared to European populations where evidence of H. Pylori is rarely found before age 10 but increases to 10 % in those between 18 and 30 years of age and to 50 % in those older than age 60 [3]. In many developing countries, the infection has a high prevalence rate (80 --95%) [5]. More than 50% of children are infected by the age of 10 years with the prevalence of infection rising to over 80% in young adults [6]. The incidence of H. pylori infection in Ghanaian patients with dyspeptic symptoms referred for upper gastrointestinal endoscopy at the Korle-Bu Teaching Hospital (KBTH) has previously been found to be 75.4% [7]. The exact mode of transmission is unclear but intrafamilial clustering suggests person-to-person spread mainly in childhood [4]. The risk of infection with H. Pylori is related to socioeconomic status and living conditions in early life. Overcrowded conditions associated with childhood poverty lead to increased transmission and higher prevalence rates [8]. Potential dietary associations with H. pylori have been investigated in humans and chronic excessive salt intake has been shown to enhance H. pylori colonization in mice and in humans [9].This study investigated the epidemiological characteristics of H. pylori infection in a West African country with a known high prevalence of the condition. detached (a single house in an enclosed compound); semi-detached (two houses built side by side and sharing a common wall); compound structure (more than two separate houses enclosed in the same compound). Urban residences were categorized into class

Results
The sample population of dyspeptic patients attending the Endoscopy Unit for upper GI endoscopy yielded 242 patients of which 47.5% were females, 52.5 % males. The overall prevalence of H. pylori obtained by immediate CLO-testing of gastric antral biopsies was 74.8%. The age distribution of H. pylori-CLO-positive cases was even across most age -groups as illustrated by Figure   1. Age group 21--30 years had the highest H. pylori prevalence, 80.0% (n=24) while age group (61--70) had the lowest, 69.2% (n=27). There was no statistically significant difference in H.
pylori prevalence between age groups, (p = 0.957). Table   1 illustrates the relationship between housing characteristics and H. pylori prevalence including number in household, type of household and residential location. There was a statistically significant difference between residential classes in relation to H. pylori prevalence (p=0.046) with rural areas having the highest prevalence (88.6%, n=39). However, H pylori prevalence decreased across areas mapping to the three residential classes in accordance with increasing affluence ( Table 1)

Discussion
The prevalence of H. pylori infection in this study was 74.8% comparable to previous studies in Ghana [7], Nigeria [10] and other developing countries [8]. The uniformly high age-related H.
pylori prevalence demonstrated supports the notion that the rate of acquisition of infection is predominantly highest in early life [11].
Indeed, it is widely believed that once acquired colonization persists throughout life unless otherwise eradicated [11]. Re-infection with H. pylori following successful bacterial cure is not uncommon in developing countries, occurring in approximately ~ 12% of individuals shown to have been originally cleared of this bacterium.
By contrast, in developed countries~1% such individuals are subsequently re-infected. Additionally, when re-infection occurs this has most commonly been shown to represent recrudescence of the original bacterial strain [12]. Studies based in Peru and Mexico showed re-infection rates of 3--7% [13,14], while in comparison a European-based study elicited a rate of only 0.4% [15]. Re-infection from multiple sources of infection in developing countries, particularly in endemic areas has also been suggested as important in maintaining the presence of this organism during adulthood [8,13,14].  [24]. Laboratory studies have experienced difficulty in isolating H. Pylori from material other than gastric tissue which has made identification of portals of entry and exit problematic [25].
Reports using whole-cell enzyme-linked immune-absorbent assay (ELISA) sonicate to monitor infection serologically, have cited a high incidence of H. pylori in abattoir workers [24]. These results have been thought to be confounded by potential antigenic crossreactivity in workers´ sera due to the constant exposure to other gastrointestinal flora of animals [24]. Thus, the isolation of H.
pylori from the inflamed gastric lining of commercially reared animals [26], and the ability to experimentally infect cats with H.
pylori [24], continues to raise the possibility of zoonotic H.
pylori transmission from infected animals who have close human contact.

Conclusion
H. pylori is endemic in Ghana but the persistently high prevalence across age groups despite significant community anti-microbial use and abuse [27], suggests likely re-crudescence or re-infection from multiple sources in a developing country. Socio-cultural factors such as residential class and farming may be facilitating factors for its continued prevalence. Further study will evaluate the impact of these epidemiological factors, broader host traits and microbial determinants in the transmission and persistence of H. pylori in Ghana.

Competing interests
The authors declare no competing interests.

Authors' contributions
Timothy Archampong, the principal investigator of the project, was  Tables and figure   Table 1: Housing characteristics and Helicobacter pylori prevalence   side and sharing a common wall); compound structure (more than two separate houses enclosed in the same compound) † Urban residences categorized into class 1 --3 based on the Accra Metropolitan Assembly (AMA) classification of Accra with tax imposition rates of Ghana Cedi (GHC) 100, GHC 60 and GHC 40 respectively The relationship between occupation and prevalence of H. pylori infection  Logistic regression analysis to demonstrate relative risk of H. pylori infection with specific predictor variables Figure 1: Age distribution of Helicobacter pylori cases