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Oct. 29 story misreported facts

By Neil H. Mendelson
Arizona Daily Wildcat
November 6, 1998
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To the editor,

When I was working at the Medical Research Council's Microbial Genetics Research Unit in London in the 1960's pathogenic bacteria were isolated from some very sick people who did not get better when given antibiotics. These isolates were among the first dangerous bacteria discovered that were resistant to drugs commonly used to help people survive life-threatening infections.

Thirty years later, things have gotten worse because the genes that govern the biochemical mechanisms responsible for the protecting the bacteria from antibiotics have rapidly spread around the world.

This is what UA Provost Paul Sypherd was talking about last week and not "human resistance to antibiotics," as reported in the Wildcat Oct. 29 issue.

Briefly, the facts are as follows:

1. Antibiotics affect bacterial cells, not human cells because their targets are unique bacterial components.

2. Bacteria can become resistant to antibiotics by changing their targets or preventing the drug from getting to the target or by producing something that destroys the antibiotic.

3. Bacterial resistance mechanism are dependent are dependent on the bacteria upon the bacteria having special genes.

4. Unlike most bacterial genes resistance genes are usually found on special DNA molecules called plasmids.

5. Many plasmids are sex factors, which means that they can transfer a copy of themselves to another bacterial cell if the two cells come into contact with another. Herein lies the problem. The bacterial cell that gets a copy of the plasmid can also make another copy of it and transfer the new copy to a third cell and so on.

6. Making things even worse, plasmids can acquire new genes by a genetic recombination mechanism and thus end up containing a collection of genes that provide resistance to many antibiotics.

7. The inappropriate use of antibiotics, for example, to treat a minor infection, is believed responsible for the rapid spread of drug resistance genes because it kills bacterial cells in us that are not dangerous and permits only resistant bacteria to survive.

8. Unfortunately, plasmids that carry drug resistant genes can reside in non-pathogenic bacteria in a healthy individual, then transfer to a newly invading pathogen wen a person becomes infected. In other words, reservoirs of drug-resistant plasmids reside in harmless bacteria that are in all of us, whether healthy or not.

What to do about all of this is a topic of great concern. Some believe that the antibiotic era is rapidly coming to an end. Others are optimistic, however, that new antibiotics can still be developed.

Whether or not they will be is to some extent a matter of economics. It is very expensive to develop new antibiotics. Alternate approaches must also be considered such as the use of vaccination to prevent infection, or the stimulation of the immune system in other ways so that an infected person cures him or herself. In this battle between humans and the microbial world, the ultimate winner remains to be determined.

Neil H. Mendelson
Professor, molecular and cellular biology