darwinian medicine

Shan Putnam sputnam at tfb.com
Thu Oct 12 19:14:18 EST 1995

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, 
> 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

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