On May 30, 2:14*pm, Andy Champ wrote:

Well, I'm censored large number years out of date but...

I guess the effect of this stuff is to punch holes in the cell
membranes. *Enough holes, no cell. *So if there's enough to punch a few
holes, but not actually kill it, and there's some variation in the
ability of the bugs to fix the holes, why would you not have selection
for something able to survive in a weak concentration? *And then they
can gradually work their way up the drain to the source of the poison
where the concentrations are higher and nothing else can survive.

After all that's the way antibiotic resistance has been bred.

Andy

I think penicillin acts in a different manner to stuff like bleach and
p/acid. But I still remain open to the possibility of a resistance to
it, I am not an expert, and am happy to accept the evidence.