Patrick O'Brian Discussion Forum

Antibiotics and resistance thereto

Mark Henry

Here are two articles on the topic:

A short, but key, quote from this article: (emphasis added)

The use of antibiotics is the single most important factor leading to antibiotic resistance around the world. †Simply using antibiotics creates resistance.

From this article:

Acquired Resistance

Bacteria can also acquire resistance. This happens when a type of bacteria changes in a way that protects it from the antibiotic. Bacteria can acquire resistance in two ways: either through a new genetic change that helps the bacterium survive, or by getting DNA from a bacterium that is already resistant.

Genetic Change

So how can a simple DNA change protect bacteria from antibiotics? Remember, DNA provides instructions to make proteins, so a change in DNA can cause a change in a protein. Sometimes this DNA change will affect the proteinís shape. If this happens at the place on the protein where an antibiotic acts, the antibiotic may no longer be able to recognize where it needs to do its job.

Changes like this can prevent an antibiotic from getting into the cell, or prevent the antibiotic from working once itís inside. Once a change occurs, it can spread in a population of bacteria through processes like reproduction or DNA transfer.

On Wed Apr 19, Bob Bridges wrote
>It occurs to me that someone here may be able to answer a question I've had running through my head for a few years now. †We're told that we shouldn't use antibiotics too freely, because they lead to the proliferation of organisms that are resistant to them. †It seems to me that this must be a misunderstanding.

>To be sure, antibiotics kill off organism that are not resistant, and fail to kill off those that are, and as a direct result the resistant organisms are a higher percentage of the total over time. †But the antibiotics didn't create the resistance, nor increase the numbers of the resistant organisms.

>Put it this way: †Let's say you start with 100 resistant bacteria and 2000 non-resistant ones. †At the end of a certain period of time they would multiply by a factor of (say) a million, at which point you'd have 100 million resistant bacteria and 2 billion non-resistant. †Or, if you use antibiotics freely, you have 90 million resistant bacteria (assuming they're slightly susceptible to antibiotics) and 200 thousand non-resistant (assuming you can't get 'em all). †So sure, the percentage of resistance went from 4.8% to 99.8%, but you're still better off by having eliminated 95.7% of the target organisms.

>So can someone, akatow or someone, tell me what I'm missing?

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