Table 2 H. pylori reservoirs.

Food

   - 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]

   - 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]

   - Sheep and cow milk can be vehicles for transmission.

See below (under Animals)

[118, 119]

Animals

   - Several animal species were suggested as H. pylori reservoirs.

H. pylori was isolated from:

- pigtailed monkeys

[120]

- rhesus monkeys

[121]

- cats

[122]

- sheep

[123]

- cockroaches

[124]

- houseflies (but the housefly hypothesis was challenged)

[125, 126]

   - 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.

[127, 128]

In Colombian Andes, children who had contact with sheep had higher prevalence odds.

[99]

Dore et al. stated that animals, especially sheep and dogs, could transmit H. pylori to humans (shepherds) in Sardinia.

[129]

   - H. pylori can be recovered from animal products.

H. pylori was recovered from sheep and cow milk.

[118, 119]

   - Experimental animal colonization is possible.

Bacillary forms of H. pylori were used to colonize germ-free piglets.

[130]

Water

   - 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.

[105, 131, 132]

   - Water from running, municipal, and underground sources, as well as wastewater has been suggested as reservoir for H. pylori.

- Municipal water

[105]

- Well water

[133]

- Running water

[99, 134]

- Wastewater

[135]

- H. pylori even survives in chlorinated water.

[136]

   - H. pylori proteins and DNA can be detected in water.

- by immunological methods

[137]

- by PCR

[133, 138]

- by hybridization methods

[139]

   - Viable H. pylori can be detected and isolated from water.

- as individual cells

[140]

- associated with biofilm

[141, 142]

- cultured

[135]