Science Update - Bacteria and You

13 May 2007

Interview with 

Chelsea Wald and Bob Hirshon


Bob -   This week for the Naked Scientists, we're going to get up close and personal with bacteria. In fact, you're up close and personal with bacteria all the time, so it's important for scientists to figure out just how we interact with them. I'm going to talk about how bacteria could help with asthma, but first, Chelsea's here to tell us about your first line of defense against harmful bacteria--skin.Campylobacter

Chelsea -   If the common staph bacterium could easily get through your skin, you'd wake up every day with disgusting sores. Now new research identifies a key agent in repelling this menace. Donald Leung's team at the National Jewish Medical and Research Center in Denver found that skin cells make a protein called human beta defensin-3 as soon as they notice harmful bacteria. The protein breaks down the bacteria's membranes, killing them. Then the skin cells encase and digest the bacteria's remains.

Donald Leung (National Jewish Medical and Research Center):  It literally happens in minutes and is probably the reason why most normal people do not have problems with bacterial infection even though our environment is teeming with bacteria.

Chelsea -   Leung says a deficiency in beta defensin-3 could help explain infection-prone skin and open a new direction for antibiotic drug development.

Bob -   Thanks, Chelsea. A common stomach infection called Helicobacter pylori may protect against childhood asthma and allergies.  This according to a new study led by microbiologist Martin Blaser, chair of the New York University Department of Medicine.  Blaser says that Helicobacter infections have been almost universal in humans for thousands of years.  But in the 20th century, the infections started disappearing, probably because of the widespread use of antibiotics.

Martin Blaser (New York University):  So, as a result, we now have people - I think for the first time in human history - adults, who either have the organism  or don't, and so we can measure the consequences.

Bob -   The bug has already been shown to have both costs and benefits to the gastrointestinal tract. Now, Blaser's team has analzyed the medical records of about 8,000 people, and found that those with Helicobacter infections are 40 percent less likely to ever have had childhood asthma or allergies.

As to why, Blaser suspects that a chronic Helicobacter infections keeps the immune system occupied, reducing the likelihood that it'll go haywire over pollen or cold air.  This is a variation of the so-called hygiene hypothesis: that by eliminating germs with our arsenal of disinfectants, we're leaving our immune systems with nothing to do, so they attack the wrong things. But Blaser suspects that the germs in our bodies matter a lot more than those on our kitchen counters.

Blaser -   When a parent takes their child to have their ear infections treated, I think that one of the hidden consequences of antibiotic use is that it's having an effect on bacteria all over the body, including in some kids, eliminating Helicobacter.  So it is possible that any time a child gets a course of antibiotics for any reason, they are marginally increasing their risk of asthma.

Bob -   The next step is to find out if people who take more antibiotics during their childhood are more likely to develop asthma or allergies than others.

Chelsea -   Thanks, Bob. Next time, we'll be back with more stories for your pleasure and that of your resident bacteria. Until then, I'm Chelsea Wald...

Bob -   ...and I'm Bob Hirshon, for AAAS, The Science Society. Back to you, Naked Scientists...


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