Abstract
Background
Helicobacter pylori has a high infection rate, and it is possible that more than half of the world's population is infected. The route of transmission of H. pylori has not been completely elucidated yet. The coccoid form of H. pylori is generally considered to be in a VBNC (viable but nonculturable) state, and this form in the environment is thought to play an important role in infection and transmission, but its stability and survivability are still unknown.
Materials and methods
In order to promote its changing to coccoid form, the spiral form of H. pylori grown in a culture medium was exposed to sterile distilled water, and we investigated the bacterial cell number and the morphological changes by using fluorescence staining methods and electron microscopic observation. We also examined the dynamics of its growth ability by measuring the colony forming unit on an agar-plate medium.
Results
After exposure to sterile distilled water, the H. pylori spiral form rapidly lost its growth ability at 37°C. One day after exposure, approximately 95% of the spiral form disappeared and the proportion of the coccoid form increased. The total number of bacteria also decreased to less than half and continued to decrease over time. Epi-microscopic and electron microscopic observations revealed that deformation of bacterial cells, collapse, and leaking out of cell contents were promoted in exposure to sterile distilled water.
Conclusion
Helicobacter pylori quickly begins to transform into the coccoid form after exposure to sterile distilled water, rapidly loses its growth ability, and then lyses and dies. Water-exposure is lethal for H. pylori and it is unlikely to survive in the VBNC state in water.
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