Failure To Detect Helicobacter pylori DNA in Drinking and Environmental Water in Dhaka, Bangladesh, Using Highly Sensitive Real-Time PCR Assays

Abstract

The main transmission pathway of Helicobacter pylori has not been determined, but several reports have described detection of H. pylori DNA in drinking and environmental water, suggesting that H. pylori may be waterborne. To address this possibility, we developed, tested, and optimized two complementary H. pylorispecific real-time PCR assays for quantification of H. pylori DNA in water. The minimum detection level of the assays including collection procedures and DNA extraction was shown to be approximately 250 H. pylori genomes per water sample. Using our assays, we then analyzed samples of drinking and environmental water (n ‫؍‬ 75) and natural water biofilms (n ‫؍‬ 21) from a high-endemicity area in Bangladesh. We could not identify H. pylori DNA in any of the samples, even though other pathogenic bacteria have been found previously in the same water samples by using the same methodology. A series of control experiments were performed to ensure that the negative results were not falsely caused by PCR inhibition, nonspecific assays, degradation of template DNA, or low detection sensitivity. Our results suggest that it is unlikely that the predominant transmission route of H. pylori in this area is waterborne.Helicobacter pylori is the most common human bacterial pathogen in the world (15), and it has been estimated that 50% of the world's population is infected. The prevalence of H. pylori infection varies greatly worldwide, with infection rates of more than 80% in some developing countries and below 20% in some developed countries (29). H. pylori causes peptic ulcers in 10 to 15% and stomach cancer in another 1 to 2% of those infected (29).H. pylori naturally resides in the human stomach, and except for some primate species, no other host has been identified. Outside its host, H. pylori is fastidious and can grow only under microaerophilic conditions at 34 to 40°C in nutrient-rich media (29). Under suboptimal conditions, H. pylori transforms into nonculturable spherical or coccoid forms. To date, it is not clear if this process is reversible or if the coccoid form is infectious or even viable, but it has been reported to retain some metabolic activity, its genome, and an intact membrane (1,6,12,28,38,47).Transmission of H. pylori has been proposed to occur via gastric-oral, oral-oral, or fecal-oral routes, with studies suggesting transmission through saliva and dental plaque (14, 23), normal and diarrheal stools (18,23,41,43), and vomitus (30, 41). Infected mothers or older siblings, low standards of living, and crowded households have been shown to be major risk factors for contracting H. pylori (25,35,50). Other studies have shown a relation between infection, water sanitation, and drinking water sources (24, 26, 39), further supported by reports of H. pylori DNA in drinking, river, lake, or seawater (3, 7, 16, 19-22, 25, 33, 34, 37, 40, 43, 49).Since none of the latter group of studies have shown a causative relation between traces of H. pylori in water and new infections, our original aim was to perform ...

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CD4+ regulatory T cells in gastric cancer mucosa are proliferating and express high levels of IL-10 but little TGF-β

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Helicobacter pylori Infection of the Gastric Mucosa

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