Table 2 |
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H. pylori reservoirs. |
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Hypothesis |
Evidence/Example studies |
Ref. |
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Food |
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- Contaminated food prepared under unhygienic conditions is a probable mechanism for transmission. |
A positive correlation was reported between prevalence of infection and consumption of food from street vendors in Peru. |
[70] |
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- The daily amount of raw vegetables is a risk factor, which possibly implies a role for water too. |
In the Colombian Andes, frequent consumption of raw vegetables was associated with likelihood of infection. |
[99] |
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- Sheep and cow milk can be vehicles for transmission. |
See below (under Animals) |
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Animals |
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- Several animal species were suggested as H. pylori reservoirs. |
H. pylori was isolated from: |
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- pigtailed monkeys |
[120] |
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- rhesus monkeys |
[121] |
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- cats |
[122] |
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- sheep |
[123] |
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- cockroaches |
[124] |
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- houseflies (but the housefly hypothesis was challenged) |
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- Working with animals may increase risk, and animal-to-human transmission is possible. |
H. pylori was suggested as zoonotic, occupational infection to meat and abattoir workers. |
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In Colombian Andes, children who had contact with sheep had higher prevalence odds. |
[99] |
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Dore et al. stated that animals, especially sheep and dogs, could transmit H. pylori to humans (shepherds) in Sardinia. |
[129] |
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- H. pylori can be recovered from animal products. |
H. pylori was recovered from sheep and cow milk. |
|
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- Experimental animal colonization is possible. |
Bacillary forms of H. pylori were used to colonize germ-free piglets. |
[130] |
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Water |
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- Water contamination is a risk factor for H. pylori infection. |
Many reports, mostly from developing countries, suggested contaminated water sources as risk factors. Examples include studies performed in Peru, Chile, and Kazakhstan. |
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- Water from running, municipal, and underground sources, as well as wastewater has been suggested as reservoir for H. pylori. |
- Municipal water |
[105] |
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- Well water |
[133] |
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- Running water |
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- Wastewater |
[135] |
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- H. pylori even survives in chlorinated water. |
[136] |
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- H. pylori proteins and DNA can be detected in water. |
- by immunological methods |
[137] |
|
- by PCR |
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- by hybridization methods |
[139] |
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- Viable H. pylori can be detected and isolated from water. |
- as individual cells |
[140] |
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- associated with biofilm |
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- cultured |
[135] |
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Examples of studies on different environmental sources of H. pylori and their role in H. pylori transmission. |
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Khalifa et al. Gut Pathogens 2010 2:2 doi:10.1186/1757-4749-2-2 |
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