Garth, did you say what you really mean:
 
>Where a gene for resistance is present it moves very rapidly from
bacterial host to host, and soon it destroys the usefullness of an
antibiotic.
<
 
It is one thing to speak of the offspring having a favorable gene, of an
evolutionary and reproductive advantage.  This sentence, however appears
to be claiming that a gene is transferred among existing bacteria, no
reproduction involved. They-do-it-themselves gene splicing, if you will.
 
Is that what you mean?
 
Mike