New Evidence Linking Water to Stomach Cancer:
on Helicobacter pylori
Kelly A. Reynolds, Ph.D.
Helicobacter pylori (H. pylori) is a spiral
shaped bacterium that makes its home in the gastric mucus layer,
or the cell lining, of the human stomach. As the bacteria colonize
the stomach, the lining is weakened and vulnerable to irritation
from natural stomach acids. The result-an ulcer.
H. pylori causes about nine out of 10 duodenal
ulcers, and more than eight of 10 gastric ulcers. A clear link has
been established associating long-term infection with H. pylori
to the development of gastric cancer, the second most common
cancer worldwide. Such cancer is especially prevalent in Colombia
and China where H. pylori is found to infect over half of
the population in early childhood.
Prior to the discovery in 1982 by two Australian physicians, Robin
Warren and Barry Marshall, that H. pylori was linked to ulcers,
the disease was thought to be caused by stress or even spicy foods.
It wasn't until 1994 that the medical community acknowledged the
strong association between the bacterium and ulcer disease. In 1995,
only 5 percent of ulcer patients were receiving antibiotic therapy.
The first antibiotics for H. pylori treatment were approved
by the U.S. Food and Drug Administration (FDA) in 1996. The next
year, the Centers for Disease Control and Prevention (CDC) launched
a nationwide campaign educating the public that ulcers are a curable
For more information
on Helicobacter pylori, visit the National Foundation
on Infectious Diseases website: http://www.nfid.org/library/recommended/helicobacter.html
Following are other related
sites of interest:
- The Helicobacter Foundation:
- Canadian Helicobacter
pylori Susceptibility Study 2000: www.helicobactercanada.com/
- Virtual Hospital: www.vh.org/providers/teachingfiles/GIAtlas/pages/2-Stomach
Populations at risk
Approximately two-thirds of the world's population is infected with
H. pylori. An estimated 2.5 million new H. pylori
infections occur each year in the United States. Associated costs
for peptic ulcer disease-affecting nearly 5 million people-exceeds
$4 billion for treatment alone. Approximately 16,000 people die
annually from the affliction.
In countries with
poor sanitation, 90 percent of the adult population are infected
with H. pylori. About 30-to-60 percent of the people in the
United States, Europe and Australia harbor H. pylori in their
stomachs. Certain factors are known to predispose populations to
increased H. pylori infections. In the United States, H.
pylori is more prevalent among older adults, African Americans,
Hispanics and lower socioeconomic groups. In underdeveloped areas,
infections are more commonly found in children whose mothers and/or
older siblings were infected. Children attending nursery school
were also more likely to become infected. H. pylori is primarily
acquired in infancy (under 2 years of age).
Most infections of
H. pylori are chronic and asymptomatic, with an estimated
one in six actually developing ulcers. Symptoms range from nausea
and vomiting to bloating and abdominal pain. Diagnosis of the infection
is achieved by a blood antibody test, urease breath test or gastrointestinal
endoscopy and biopsy. Although controversial, other implications
of H. pylori infections have been suggested including a potential
cause for skin rashes, SIDS (sudden infant death syndrome) and reactive
While five H. pylori
treatment regimens have been approved by the FDA, certain strains
of the organism have developed resistance to one or more antibiotic
treatments. One study showed that as many as 42 percent of patients
with H. pylori infections didn't respond to at least one
of the recommended antibiotic treatments.2 The highest treatment success rates (70-to-90
percent cured) have been found from a combined three-drug regimen.
Evidence of waterborne
Researchers have looked for H. pylori in tap and well water,
cow feces, flies and field soil samples in Japan, where the incidence
of infection was high. All sample categories were found to harbor
the bacterium. Although the organism appears to be nearly ubiquitous
in natural environments, the primary transmission route has yet
to be determined. Also a mystery is why some infections manifest
as clinical symptoms, while others go unnoticed.
The bacteria are most likely spread via person-to-person either
through the fecal-oral or oral-oral routes. Successful isolation
of H. pylori from stools of infected people is evidence of
a likely fecal-oral route, where contaminated food and water are
suspected reservoirs. Increased prevalence of infection has been
associated with consumption of food from street vendors, suggesting
that improperly prepared foods may play a role in transmission of
H. pylori infections. In addition, H. pylori has been
found in more than 75 percent of tested surface water samples, indicating
that the organism is pervasive in drinking water sources.
In May 1999, at the
99th meeting of the American Society for Microbiology in Chicago,
a research team from Penn State Harrisburg, lead by Dr. Katherine
H. Baker, presented the first direct link found between bacteria
in drinking water and stomach ulcers.3 Interviews with residents that drank water from
private, untreated well supplies revealed there was a significant
correlation between presence of H. pylori and cases of stomach
Once in the stomach,
H. pylori may also be transmitted to the mouth via reflux
action where a portion of the stomach's contents is forced up the
esophagus. The organism has also been isolated from dental plaque
of 30 percent of people with gastric infection.
Methods for direct culture detection of H. pylori haven't
been fully developed. Part of the difficulty in detecting this pathogen
is that changes in cell morphology, metabolism, and growth patterns
occur when the organism is exposed to different environmental stimuli,
including the condition of viable but non-culturable organisms.
This phenomenon has been described in association with other bacteria
such as Vibrio cholerae, the agent that causes cholera. Viable
but non-culturable organisms are particularly worrisome because
they're capable of eluding conventional culture analysis, falsely
indicating safe water. Non-cultural methods of detection may be
used such as microscopy or molecular methodologies, but these are
often limited by interfering compounds and small equivalent volumes.
In addition, they don't determine if the organism is viable, and
thus a threat to humans. H. pylori is known to survive in
tap water for up to four days; however, the viable but non-culturable
form may survive nearly twice as long.
The water industry
has relied on bacterial indicators-coliform bacteria-to evaluate
the safety of source waters for decades. Unfortunately, H. pylori
is commonly found in waters where coliform indicators were absent.
The high prevalence of H. pylori in the limited number of monitoring
efforts to date indicate an urgent need for the development of rapid,
specific and reliable detection methods in order to evaluate the
potential impact of the waterborne role in H. pylori infections.
A need for water
The good news is that H. pylori is sensitive to conventional
methods of water treatment (i.e., chlorination) and thus isn't thought
to be a problem with properly treated water supplies.4 Yet, studies using ultraviolet light or ozone
aren't in great abundance. In addition, proper antibiotic treatment
can completely eradicate the organism, with little chance of its
reoccurrence. Treatment of asymptomatic patients with H. pylori
infections isn't warranted unless there is a history of gastric
cancer or chronic H. pylori infections in the family. Preventative
programs of vaccination in early childhood may be available in the
Since the source of H. pylori is still under investigation,
the CDC recommends that people continue to practice methods of good
hygiene by washing hands frequently and thoroughly, eating food
that has been properly prepared and drinking water from a safe,
clean source. Stomach cancer in the United States is now one-fourth
as common as it was in 1930. Improved sanitation and water treatments
are thought to be the main reasons for the reduction.
1. Centers for Disease Control and Prevention (CDC), "Fact
Sheet on Helicobacter pylori," 2000: www.cdc.gov/ncdod/dbmd/md.htm
2. Mendonca, S. et
al., 2000, "Prevalence of Helicobacter pylori resistance
to metronidazole, clarithromycin, amoxicillin, tetracycline, and
furazolidone in Brazil," [In Process Citation], 5:79-83, 2000.
3. Baker, K., "Researchers find link between contaminated water
and stomach ulcers," Proceedings of the 99th General Meeting
of the American Society for Microbiology, Session 241, Paper Q319,
Chicago, May 30-June 3, 1999.
4. Johnson, C.H. et
al., "Inactivation of Helicobacter pylori by chlorination,"
Applied Environmental Microbiology, 63:4969-4970, 1997.