Transcript 04ANTIBIOTIC RESISTANCE

ANTIBIOTIC
RESISTANCE
© 2008 Paul Billiet ODWS
Fast breeders


Bacteria reproduce
very quickly
Eschericia coli can
complete a life cycle in
30 minutes
E. Coli
© 2008 Paul Billiet ODWS
Sex in bacteria





Bacteria do exchange genes forming new
combinations
Bacteria exchange genes is 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
© 2008 Paul Billiet ODWS
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
It 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
© 2008 Paul Billiet ODWS
Resistance
It took less than 20 years for, bacteria to
show signs of resistance
 Staphylococcus aureus, which causes
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

© 2008 Paul Billiet ODWS
Multiple resistance
It seems that some resistance was already
naturally present in bacterial populations
 The presence of antibiotics in their
environment in higher concentrations
increased the pressure by natural
selection
 Resistant bacteria that survived, rapidly
multiplied
 They passed their resistant genes on to
other bacteria (both disease causing
pathogens and non-pathogens)

© 2008 Paul Billiet ODWS
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

© 2008 Paul Billiet ODWS
Antibiotics promote resistance







If a patient taking a course of antibiotic
treatment does not complete it
Or forgets to take the doses regularly,
Then resistant strains get a chance to build up
The antibiotics also kill innocent bystanders
bacteria which are non-pathogens
This reduces the competition for the resistant
pathogens
The use of antibiotics also promotes antibiotic
resistance in non-pathogens too
These non-pathogens may later pass their
resistance genes on to pathogens
© 2008 Paul Billiet ODWS
Resistance gets around
When antibiotics are used on a person,
the numbers of 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 in
numbers

© 2008 Paul Billiet ODWS
Antibiotic use and abuse
Viral infections are not stopped by
antibiotics
 Yet doctors still prescribe (or are coerced
into prescribing) antibiotics to treat them

© 2008 Paul Billiet ODWS