Since I'm on that topic, i.e. recognition of emerging pathogens of infectious diseases, there is another which is a favorite of mine, Helicobacter pylori. Again, some of you may have had the unfortunate experience of being infected with Helicobacter pylori which causes ulcers in humans. Now there is a strong connection with its further association with gastric cancer. The reason I'm mentioning Helicobacter now is because the Chlamydia story has a lot of sounds that ring like Helicobacter. Helicobacter couldn't be grown very well. It was growing in the stomach and we said wait a minute!? Just as Lynn mentioned this morning with the pH, how can a creature survive the low pH found in the stomach? Stomach hydrochloric acid, producing a pH of two, maybe lower, how can that creature grow? It grows because it produces an enzyme that can hydrolyze urea. It's called urease. When it actually takes blood urea and hydrolyses it to form carbon dioxide and ammonia.

In fact, that's the basis of one of the diagnostic tests currently used. They can give a patient radioactive urea and look for the exhaust of radiolabeled carbon dioxide. Before the availability of the new test, endoscoping was done. Gastroenterologist still use this procedure which is not so pleasant, requiring placement of the tube down the throat and into the stomach. You've got to swallow that thing; then a piece of tissue is taken from the stomach to do a culture. Even with that tissue we can do PCR now, rather than waiting to isolate the organism. Heliobacter is still not so easy to grow. In summary then, PCR is a very useful technique for identification of bacteria which are difficult to isolate and the enzyme currently used in PCR is just a very important offshoot of some of the benefits that we get from some of these extreme organisms.

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