Survival of Helicobacter pylori in a Natural Freshwater Environment

Abstract

The mode by which Helicobacter pylori, the causative agent of most gastric ulcers, is transmitted remains undetermined. Epidemiological evidence suggests these organisms are waterborne; however, H. pylori has rarely been grown from potential water sources. This may be due to the ability of this organism to rapidly enter the viable but nonculturable (VBNC) state. Our investigation examines the entrance of H. pylori into this state in laboratory cultures and a natural freshwater environment as well as the relationship between morphology and culturability. To this end, membrane diffusion chambers were utilized to expose the cells to the natural fluctuations of a freshwater stream. In both the laboratory and environment, samples were assayed for culturability using plate counts and stained using a LIVE/DEAD BacLight assay for viability and morphological determinations. Additionally, water samples were collected, six environmental parameters were measured, and resuscitation conditions were examined. H. pylori was observed to lose culturability in the laboratory and stream, although viability was maintained. While the results of our study agree with those of previous studies which suggested that there is a transition in morphology from rods to cocci as culturability is lost, the morphological distribution of cells did not change as culturability was lost in the environment. The majority of cells in the VBNC state in the laboratory are cocci; however, all morphological forms were present in the environment. The results of these studies suggest that H. pylori persists in laboratory cultures and the environment in the VBNC state and that cells in this state represent a public health hazard.Infection by the gram-negative microaerophilic rod Helicobacter pylori is associated with the development of chronic human gastritis, peptic ulcers, and gastric adenocarcinoma (2,5,26). It has been estimated that more that half of the world's population is infected with this organism (18). Despite such a high incidence of infection, the bacterium's reservoir and mode of transmission remain undetermined. Molecular methods have detected the presence of H. pylori DNA in river water, well water, and wastewater as well as in surface and shallow groundwater, suggesting that this organism is waterborne and might be transmitted by the fecal-oral route (12,14,22). However, only a single study has been published which claims that isolation of H. pylori directly from environmental sources had been performed and that the isolation occurred only following immunomagnetic separation of the cells from raw sewage (20).It has been postulated that the inability to culture H. pylori from the environment is due to its entrance into the viable but nonculturable (VBNC) state. Cells that have entered this state are no longer culturable on routine bacteriological media, although they remain viable (25). Entrance of the bacterium into the VBNC state is induced by a variety of adverse conditions, such as temperature downshift or nutrient depletion (25). The entr...

Shear Stress, Temperature, and Inoculation Concentration Influence the Adhesion of Water-Stressed Helicobacter pylori to Stainless Steel 304 and Polypropylene

“…It has been described that the bacterium remains culturable for much longer in water at low temperatures (22 days at 4°C) than at high temperatures (6 to 10 h at 23°C) (1,4,25). The results of culturability tests performed on planktonic cells in one of our experiments at 23°C agreed with this observation, with a loss of culturability being observed after 6 h (N. F. Azevedo, M. J. Vieira, and C. W. Keevil, unpublished data).…”

Physiological Characterization of Campylobacter jejuni under Cold Stresses Conditions: Its Potential for Public Threat

“…In general, this storage method has been considered an effective means of reducing the possibility of infection, however, increasing demand for long-life fresh products creates new risk such as viable but non-culturable (VBNC) bacteria in the cold chain. A number of pathogens (e.g., Escherichia coli O157:H7, Salmonella Typhimurium, Salmonella Oranienburg, Vibrio cholerae, Helicobacter pylori, Listeria monocytogenes) enter a VBNC state in response to various environmental stresses such as cold exposure, pH, and high osmolarity [2,3,8,34,40]. In a VBNC state, the bacteria cannot be detected by conventional culture-based methods due to the loss of culturability on the media that normally support their growth, but remain viable and express various degrees of metabolic activities [12,16,37].…”

Reduced infectivity of waterborne viable but nonculturable Helicobacter pylori strain SS1 in mice

“…Furthermore, H. pylori has been detected in water using various molecular biology techniques, such as quantitative polymerase chain reaction (qPCR) and microscopy methods,5, 10, 11, 12, 13 and there are reports that it has been cultured from water 14, 15, 16, 1718, 19, 20. This change is often accompanied by a morphological change from a spiral bacillus to a U‐shaped or coccoid form, and H. pylori has been found in the VBNC state in all these morphologies in the natural environment 18, 21.…”