I recently met a rather unimpressive doctor who told me that he
prescribes antibiotics for any of his patients who ask for them.
He said he knows that in many cases the drugs will do no good,
but they do no harm and if the patient wants them, he aims to
please.

There are a lot of problems with this stance given that
antibiotics can indeed have negative side effects for the
patients. But I'm particularly interested in understanding
whether this practice contributes to the evolution of antibiotic
resistant bacteria.

The doctor insisted it did not. He said that, if the people
don't have bacterial infections, they can't develop resistant
bacteria. And if they do have infections, they still won't
develop resistant bacteria unless they fail to take the full
course of therapy, typically anywhere from 10-28 days.

I don't know of any definitive studies directly addressing this issue, but I
think this practice does promote the evolution of AB resistant bacteria.
These drugs pass through patients and make it into the surrounding
environment. For example, I understand that concentrations of antibiotics
can be detected in many waterways. It presumably gets there through the
urine of patients on antibiotics. Once it is in the environment it provides
an advantage to AB resistant strains out there.

It is also probably the case that we all carry lots of bacteria all the
time. Being asymptomatic does not mean that we do not carry a population of
bacteria. By giving antibiotics to patients who don't need them we still
cultivate increasing AB resistant populations, IMHO.

Cheers,

Guy

in article f3n0nr$b6i$1@darwin.ediacara.org, Alan Meyer at ameyer2@yahoo.com
wrote on 5/31/07 10:30 AM:

On 31 Mag, 19:30, "Alan Meyer" yahoo.com> wrote:

I don't have hard citations on this. However, you asked for an
opinion so I'll give one that I hope sounds educated based on general
principles of evolution.
I think that they are a little bit wrong when they say that
antibiotic resistance can't develope if the course of teatment is
followed to the very end. However, their course of treatment may be
the best of possible evils. Allow me to expand.
I think that they are assumming that their course of treatment
will kill each and every relevant bacterium in the body. A general
principle in evolution is that evolution rarely or never occurs in
sudden jumps. Therefore, an intense treatment by antibiotics can in
principle kill each and every bacterium in the body. There is no way a
bacterial variety can arise if each and every bacterium in the body is
annihilated. The bacterial population doesn't have enough variability
in it to assure that some bacterium will be resistant enough to
survive an intense and prolonged treatment. If bacteria do survive, ...

Alan Meyer wrote:

Genetic exchanges between bacteria were first discovered because
of antibiotic resistance. I don't have the reference, but antibiotic
resistance was discovered in a case were it accidently was transferred
from one species to another. This occurred sometime in the late 50s,
when they didn't really know much about DNA. I don't know if this type
of experiment is still legal, but for a while antibiotic resistance
was one of the major means of studying genetic transfer. Now, they
have other means of monitoring the transfer of genes (histoimmune
typing, DNA, etc.)
The main means of exchanging genetic material is conjugation,
where plasmids are exchanged. I am very much interested in what types
of hybridization barrier are involved in this transfer. I am sure it
is not unlimited. Your doctors may be thinking that bacteria can only
conjugate with closely related species.
Does anyone know whether true meiosis is more or less selective
than bacterial conjugation? This could be an important question with ...

On 4 Giu, 06:30, Lorentz yahoo.com> wrote:

What about the patient's risk that he may get a secondary
bacterial infection that goes out of control? A secondary bacterial
infection can do a lot of damage, more than the original viral
infection.

Alan Meyer schrieb:

An article on antibiotics and evolution:
http://www.eurekalert.org/pub_releases/2005-05/sri-tse051805.php

Regards,
Joachim

On Jun 4, 12:30 am, Bill Morse verizonOSPAM.net> wrote:

Presumably the resistant strain had a lower reproduction rate than the
sensitive wild type. That is not always the case, eg:

QUOTE
Antibiotic resistance: road of no return
by Bob Hartzler

November 1997 - The selection of resistant biotypes is a similar
process, whether dealing with weeds resistant to herbicides or
bacteria resistant to antibiotics. An article in the 24 October, 1997
issue of Science provides new insights into the persistence of
resistance within populations.