04 antibiotic resistance


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04 antibiotic resistance

  1. 1. ANTIBIOTIC RESISTANCE © 2008 Paul Billiet ODWS
  2. 2. Fast breeders <ul><li>Bacteria reproduce very quickly </li></ul><ul><li>Eschericia coli can complete a life cycle in 30 minutes </li></ul>© 2008 Paul Billiet ODWS E. Coli
  3. 3. Sex in bacteria <ul><li>Bacteria do exchange genes forming new combinations </li></ul><ul><li>Bacteria exchange genes is by conjugation </li></ul><ul><li>This involves the transfer of genetic material via a cytoplasmic bridge between the two organisms </li></ul><ul><li>This can be done between unrelated species of bacteria </li></ul><ul><li>Recent studies on bacteria in the wild show that it definitely occurs in the soil, in freshwater and oceans and inside living organisms </li></ul>© 2008 Paul Billiet ODWS
  4. 4. The magic bullet <ul><li>Antibiotics revolutionised medicine </li></ul><ul><li>The first antibiotic, penicillin, was discovered by Alexander Fleming in 1929 </li></ul><ul><li>It was later isolated by Florey and Chain </li></ul><ul><li>It was not extensively used until the 2nd World War when it was used to treat war wounds </li></ul><ul><li>After 2nd World War many more antibiotics were developed </li></ul><ul><li>Today about 150 types are used </li></ul><ul><li>Most are inhibitors of the protein synthesis, blocking the 70S ribosome, which is characteristic of prokaryotes </li></ul>© 2008 Paul Billiet ODWS
  5. 5. Resistance <ul><li>It took less than 20 years for, bacteria to show signs of resistance </li></ul><ul><li>Staphylococcus aureus , which causes blood poisoning and pneumonia, started to show resistance in the 1950s </li></ul><ul><li>Today there are different strains of S. aureus resistant to every form of antibiotic in use </li></ul>© 2008 Paul Billiet ODWS
  6. 6. Multiple resistance <ul><li>It seems that some resistance was already naturally present in bacterial populations </li></ul><ul><li>The presence of antibiotics in their environment in higher concentrations increased the pressure by natural selection </li></ul><ul><li>Resistant bacteria that survived, rapidly multiplied </li></ul><ul><li>They passed their resistant genes on to other bacteria ( both disease causing pathogens and non-pathogens) </li></ul>© 2008 Paul Billiet ODWS
  7. 7. Transposons & Integrons <ul><li>Resistance genes are often associated with transposons, genes that easily move from one bacterium to another </li></ul><ul><li>Many bacteria also possess integrons, pieces of DNA that accumulate new genes </li></ul><ul><li>Gradually a strain of a bacterium can build up a whole range of resistance genes </li></ul><ul><li>This is multiple resistance </li></ul><ul><li>These may then be passed on in a group to other strains or other species </li></ul>© 2008 Paul Billiet ODWS
  8. 8. Antibiotics promote resistance <ul><li>If a patient taking a course of antibiotic treatment does not complete it </li></ul><ul><li>Or forgets to take the doses regularly, </li></ul><ul><li>Then resistant strains get a chance to build up </li></ul><ul><li>The antibiotics also kill innocent bystanders bacteria which are non-pathogens </li></ul><ul><li>This reduces the competition for the resistant pathogens </li></ul><ul><li>The use of antibiotics also promotes antibiotic resistance in non-pathogens too </li></ul><ul><li>These non-pathogens may later pass their resistance genes on to pathogens </li></ul>© 2008 Paul Billiet ODWS
  9. 9. Resistance gets around <ul><li>When antibiotics are used on a person, the numbers of antibiotic resistant bacteria increase in other members of the family </li></ul><ul><li>In places where antibiotics are used extensively e.g. hospitals and farms antibiotic resistant strains increase in numbers </li></ul>© 2008 Paul Billiet ODWS
  10. 10. Antibiotic use and abuse <ul><li>Viral infections are not stopped by antibiotics </li></ul><ul><li>Yet doctors still prescribe (or are coerced into prescribing) antibiotics to treat them </li></ul>© 2008 Paul Billiet ODWS