Monday, June 02, 2003

Say hello to your intestinal microflora [Science News].

6/4: Nature on the impending demise of Heliobacter pylori:

But should we be in such a rush to finish Helicobacter off? Blaser argues that H. pylori may have been such an evolutionary success because it offers some advantages to its host. For one, it may protect against childhood diarrhoea -- still a major killer across large parts of the developing world -- by boosting the immune system and producing peptides that kill other bacteria.

Blaser also notes that H. pylori's wane has corresponded to an increase in acid reflux diseases -- serious forms of heartburn -- and cancers of the oesophagus. This may be because H. pylori can damp down the stomach's production of acid.

But this view is controversial. Most medics view an H. pylori infection as an unambiguously bad thing. Some believe that infection with the bacterium may even make childhood diarrhoea worse, as the lowered acid production may allow other bacteria to survive passage through the stomach. "H. pylori infection is a serious disease," says gastroenterologist David Graham of Baylor College of Medicine in Houston, Texas. "To say it has protective effects is a play on words more than anything else." Graham goes so far as to advocate pre-emptive eradication in regions where gastric cancer is common.

But even without a campaign against it, H. pylori seems to be doomed. "In the United States, it's disappearing faster than it would if we had a public-health drive to eradicate it," Parsonnet says.

H. pylori's fate has been easy to track, because it is by far the most dominant bacterium in the stomach. But many of the other 500 or so species of bacteria in our gut might be experiencing population changes without our knowledge. At the moment we can only guess at what the consequences will be. For instance, could shifts in our gut flora have anything to do with the Western world's epidemic of chronic conditions such as allergies and asthma? "Our indigenous organisms are part of our own physiology," says Blaser. "Their extinction may play a role in some of our post-modern diseases."

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