Bacteria can develop antibiotic resistance quickly through their ability to reproduce rapidly and exchange genes with other bacteria. The overuse and misuse of antibiotics applies evolutionary pressure that allows resistant bacteria to multiply, passing their resistance to other species. Within 20 years of an antibiotic's introduction, bacterial strains have often evolved resistance to it. The rise of resistant pathogens is exacerbated by incomplete treatment courses and the use of antibiotics for non-bacterial infections, as it kills benign bacteria and allows resistant strains to flourish.

1. ANTIBIOTIC
RESISTANCE
http://articles.mercola.com/sites/articles/archive/
2010/06/10/overuse-of-antibiotics-spurs-vicious-
cycle.aspx © 2016 Paul Billiet ODWS

2. Fast breeders
 Bacteria reproduce
very quickly
 Eschericia coli can
complete a life cycle in
30 minutes
E. Coli
© 2016 Paul Billiet ODWS

3. Sex in bacteria
 Bacteria do exchange genes forming new
combinations
 Bacteria exchange genes by conjugation
 This involves the transfer of genetic material via
a cytoplasmic bridge between the two organisms
 This can be done between unrelated species of
bacteria
 Recent studies on bacteria in the wild show that
it definitely occurs in the soil, in freshwater and
oceans and inside living organisms.
© 2016 Paul Billiet ODWS

4. The magic bullet
 Antibiotics revolutionised medicine
 The first antibiotic, penicillin, was discovered by
Alexander Fleming in 1929
 It was later isolated by Florey and Chain.
© 2016 Paul Billiet ODWS

5. Antibiotics
 Penecillin was not extensively used until
the 2nd World War when it was used to
treat war wounds
 After 2nd World War many more
antibiotics were developed
 Today about 150 types are used
 Most are inhibitors of the protein
synthesis, blocking the 70S ribosome,
which is characteristic of prokaryotes.
© 2016 Paul Billiet ODWS

6. Resistance
 <20 years for bacteria to
show signs of resistance
 Staphylococcus aureus
(blood poisoning and
pneumonia) started to
show resistance in the
1950s
 Today there are different
strains of S. aureus
resistant to every form of
antibiotic in use. http://www.bacteriainphotos.com/Staphylococcus%20
aureus%20electron%20microscopy.html
© 2016 Paul Billiet ODWS

7. Multiple resistance
 Some resistance was already naturally
present in bacterial populations
 Antibiotics added to their environment in
higher concentrations increased the
pressure by natural selection
 Resistant bacteria that survive, rapidly
multiplied
 Passed their resistant genes on to other
bacteria (both disease causing
pathogens and non-pathogens).
© 2016 Paul Billiet ODWS

8. Transposons & Integrons
 Resistance genes are often associated
with transposons, genes that easily move
from one bacterium to another
 Many bacteria also possess integrons,
pieces of DNA that accumulate new genes
 Gradually a strain of a bacterium can build
up a whole range of resistance genes
 This is multiple resistance
 These may then be passed on in a group
to other strains or other species
© 2016 Paul Billiet ODWS

9. Antibiotics promote resistance
 If a patient taking a course of antibiotic treatment
does not complete it (or forgets to take it)…
 the resistant strains get a chance to build up
 Antibiotics also kill innocent bystanders, bacteria
which are non-pathogens
 Reduced competition for the resistant pathogens
 Use of antibiotics also promotes antibiotic
resistance in non-pathogens too
 These non-pathogens may later pass their
resistance genes on to pathogens
© 2016 Paul Billiet ODWS

10. Resistance gets around
 When antibiotics are used on a person,
then antibiotic resistant bacteria increase
in other members of the family
 In places where antibiotics are used
extensively
e.g. hospitals and farms
antibiotic resistant strains increase.
© 2016 Paul Billiet ODWS

11. Antibiotic use and abuse
 Viral infections not stopped by antibiotics
 Doctors still prescribe (or are coerced into
prescribing) antibiotics to treat them.
© 2016 Paul Billiet ODWS