Antimicrobial Usage & Spread of Resistance -Reply

Matthew or Dawnita Nilles nilles at mis.net
Wed Jan 22 22:06:28 EST 1997

In article <s2e4e9d8.085 at war.wyeth.com>, PROJANS at war.wyeth.com (Steven
Projan) wrote:

> I've seen it written and said many times that the using antibiotics
> for treating what may be a viral infection represents a missue of
> antibiotics and is a major cause of antibiotic resistant bacteria.  

> Sorry but before I can accept the premise that bad family doctors
> writing antibiotic prescriptions for what may be a viral infection
> cause antibiotic resistance all I can say is:
> SHOW ME THE DATA!!!  And I don't mean The New York Times or that
> semi-informed, hyperbolizing, plague of a tabloid journalist Laurie
> Garrett, I mean good, solid peer reviewed, New England Journal of
> Medicine-type data.
> Steve Projan
> Wyeth-Ayerst Research
> (a big bad pharmaceutical company)


Prolonged exposure of bacteria to antimicrobial agents can and does select
for resistant bacteria.  Growth of E. coli for extended generations in the
presence of chloramphenicol or tetracycline selects for Multiple
Antibiotic Resistant (Mar) strains of E. coli (extensively demonstrated in
the basic literature).  These strains are not only resistant to tet and
cam but are also resistant to flouroquinolones and beta-lactams (and many
other compounds).  This same effect is acheived by exposure to
environmental phenolics and oxidative stress (i.e. Nitric oxide), again
this is all documented quite well.  The regulatory genetic loci
responsible (such as marA and soxRS) are found in diverse gram negative
bacteria.  The efflux pump systems responsible for most of the induced
resistance are also found in diverse bacteria (i.e. E. coli, Salmonella,
Neisseria, Haemophilus, Pseudomonas, etc.)  Granted these studies were
conducted in the laboratory, are not in clinical settings they do however,
show resistance can be induced and can be transitory.  Therefore, it seems
reasonable that improper treatment could also select for resistant strains
of (at least gram negative) bacteria.  I think that we do not understand
microbial resistance and the emergence of reistant bacteria well enough to
claim that resistant strains can't arise  from improper treatment.  Proper
studies need to be conducted so this issue can be adequeately addressed. 
In summary, I feel all physicians should critically determine if
antibiotic therapy is warranted and then prescribe an effective broad
spectrum antibiotic while culturing and determining susceptibility (almost
never done) and then adjust the treatment accordingly.  Additionally, they
should not succumb to pressures from patients to "just give me something
so I feel better".  I know this sounds like added work for M.D.s but might
it not be better to be prudent and appropriately treat infections to
decrease the real possibility of selecting for resistant bacteria.


Matthew L. Nilles
University of Kentucky
Dept. of Microbiology and Immunology

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