送交者: Latino2 于 2005-2-16, 15:12:59:
而发展中国家几乎人人都带有幽门螺旋杆菌。
幽门螺旋杆菌的消失造成发达国家居民消化道生态平衡的改变。具体表现为： 富国居民消化道溃疡和胃癌比例也随之下降，但其它疾病包
括胃酸与食道癌却急速增加。
不干不净， 吃了没病。 太干净了也不是好事。
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Helicobacter pylori is one of humanity's oldest and closest companions,
and yet it took scientists more than a century to recognize it. As early
as 1875, German anatomists found spiral bacteria colonizing the mucus layer
of the human stomach, but because the organisms could not be grown in a
pure culture, the results were ignored and then forgotten. It was not until
1982 that Australian doctors Barry J. Marshall and J. Robin Warren isolated
the bacteria, allowing investigations of H. pylori's role in the stomach
to begin in earnest. Over the next decade researchers discovered that people
carrying the organisms had an increased risk of developing peptic ulcers--breaks
in the lining of the stomach or duodenum--and that H. pylori could also trigger
the onset of the most common form of stomach cancer [see "The Bacteria behind
Ulcers," by Martin J. Blaser; Scientific American, February 1996].
Just as scientists were learning the importance of H. pylori, however, they
discovered that the bacteria are losing their foothold in the human digestive
tract. Whereas nearly all adults in the developing world still carry the
organism, its prevalence is much lower in developed countries such as the
U.S. Epidemiologists believe that H. pylori has been disappearing from developed
nations for the past 100 years thanks to improved hygiene, which blocks
the transmission of the bacteria, and to the widespread use of antibiotics.
As H. pylori has retreated, the rates of peptic ulcers and stomach cancer
have dropped. But at the same time, diseases of the esophagus--including
acid reflux disease and a particularly deadly type of esophageal cancer--have
increased dramatically, and a wide body of evidence indicates that the rise
of these illnesses is also related to the disappearance of H. pylori....