Walter Ogston wrote:
>> Scott Hoffman (schoffma at badlands.nodak.edu) writes:
>> > If a population of vancomycin resistant cells were selected
for by
> > vancomycin treatment, and then the selective pressure of
vancomycin was
> > removed, would it be resonable to believe that a population
of vancomycin
> > sensitive cells would eventually outcompete and re-establish
itself? As
> [snip]
>> I think this is a very good question. As Scott says, if
> unselected antibiotic resistance involves a metabolic cost,
then
> one would expect it to disappear from the population quite
> quickly, but if the gene is repressed and presents essentially
> no cost, then what?
>
I just finished reading Dr. Stuart Levy's book "The Antibiotic
Paradox" and he addresses this very issue (p 245-246).
Apparently the literature doesn't support the "remove the
antibiotic -- lose the resistance." He states "Since this
perstistence is not associated with the constant presence of an
antibiotic, it presumably relates to other features of the
resistance phenomenon." ie.) antibiotic resistance determinants
(whether plasmid mediatated or chromosomal) participating in
heavy metal resistance. I am presently doing a literature
search pertaining to any research looking at this prob. The
basic genetic tenents really indicated that if a genetic
component is unnecessary, then it is effectively removed (excess
baggage - energy users). However, it appears that these
multi-resistant bacteria maintain their resistance for long
periods of time, even after the removal of antibiotic.
Anyway, this book is an excellent source pertaining to the
misuse of antibiotics world-wide and the multi-resistant
bacterial implications. I highly recommend it.
Publisher -- Plenum Press, 1992
ISBN 0-306-44331-7
