MadSci Network: Microbiology

Re: Is taking the complete dose of an antibiotic really needed?

Area: Microbiology
Posted By: Eric Clambey, MadSci Admin
Date: Mon May 12 09:29:51 1997
Area of science: Microbiology
ID: 863392189.Mi
You address an interesting and extremely timely question.  

First of all, bacteria are always mutating and changing.  The ways in which
bacteria pick up new DNA (e.g. through plasmid exchange or by simply taking up
extracellular DNA) in addition to their short generation time means that bacteria
are masters at adapting to their environment.  While this is a 
naturally occurring process, in the face of strong selective pressures (e.g.
antibiotic treatment) if there happens to be a bacteria which has a mutation
which makes it resistant to the harsh conditions in the environment then that
bacteria will survive and shortly dominate the bacterial population.  Again,
this is a result of the short generation time of bacteria (in some cases, it 
only takes 20 minutes for a bacteria to divide).  

Antibiotics revolutionized the fight against bacterial infections.
Unfortunately over the past 40 years, there has been an increasing abuse of
antibiotics.  Antibiotics are put in cattle feed and people often take antibiotics
for infections that cannot be cured by antibiotics (viral infections CANNOT 
be cured by taking penicillin, for example).  In the case of antibiotics in 
cattle feed, the antibiotics have been used to prevent infections in cattle 
populations.  Nonetheless, the massive use of antibiotics has lead to
a situation today where there are an increasing number of bacteria that are 
resistant to antibiotics that worked previously.  We've seen this with a number
of bacteria (including Neisseria which causes gonorrhea and Mycobacterium 
tuberculosis which causes tuberculosis).  This has been a frightening discovery,
but in retrospect this shouldn't come as a surprise.  The plasticity of bacteria
to adapt and change to the environment (especially given their very short life
cycles!) would naturally adapt to our use of antibiotics.  Indeed antibiotics 
were first discovered as naturally occurring substances that certain bacteria, 
fungi, etc, use to kill off other bacteria.  There were natural forces selecting
for antibiotic resistance before we stumbled upon antibiotics and used them for 
our own purposes.

Your question asks whether there is any value in taking a full course of
antibiotics.  The answer is YES!  The reason that it is important to take a 
full course of antibiotics is as follows.  Antibiotics can adversely impact
the survival of specific bacteria, but an antibiotic does not kill off every
bacteria immediately.  Although during the first days of taking antibiotics 
you might kill a lot of bacteria, some of the bacteria in your system take 
longer to kill off.  Maybe they are growing more slowly and therefore are 
affected less quickly by the antibiotic.  IF YOU DO NOT TAKE THE FULL COURSE OF
easy to think you have cleared an infection when you start feeling better, but 
the full antibiotic treatment is a precaution to make sure that ALL the bacteria
are killed off in your infection.  

If anything not taking the full course of antibiotics may even facilitate 
antibiotic resistance!  When your infection comes back, you might take the same
antibiotics as you did initially.  If you don't take the full course of 
antibiotics this time, you are giving the bacteria chance after chance to mutate
in such a manner to develop antibiotic resistance.  

There is the chance that your infection is resistant to some sorts of 
antibiotics.  However, it is possible for a doctor to do tests to determine 
what the bacteria is sensitive to and what it is resistant to.  If the bacteria
is resistant to certain antibiotics, a person can usually take a different 
antibiotic which is effective against the bacteria.  

So, yes use of antibiotics has lead to antibiotic resistant bacteria.  However,
the amount of good that antibiotics have done in the past and continue to do 
today account for the reason that they are still used today.  There is also a
good basis for why you should take the full course of antibiotics.  If
you don't you might get a relapse of your infection.  You might also unwittingly
help the bacteria adapt to any attempts to heal you.  

Hope that helps.


Current Queue | Current Queue for Microbiology | Microbiology archives

Try the links in the MadSci Library for more information on Microbiology.

MadSci Home | Information | Search | Random Knowledge Generator | MadSci Archives | Mad Library | MAD Labs | MAD FAQs | Ask a ? | Join Us! | Help Support MadSci

MadSci Network
© 1997, Washington University Medical School