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ANTIBIOTIC RESISTANCE. © 2008 Paul Billiet ODWS. E. Coli. Fast breeders. Bacteria reproduce very quickly Eschericia coli can complete a life cycle in 30 minutes. © 2008 Paul Billiet ODWS. Sex in bacteria. Bacteria do exchange genes forming new combinations

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antibiotic resistance

ANTIBIOTIC RESISTANCE

© 2008 Paul Billiet ODWS

fast breeders

E. Coli

Fast breeders
  • Bacteria reproduce very quickly
  • Eschericia coli can complete a life cycle in 30 minutes

© 2008 Paul Billiet ODWS

sex in bacteria
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
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
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
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
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
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
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 farmsantibiotic resistant strains increase in numbers

© 2008 Paul Billiet ODWS

antibiotic use and abuse
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