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ANTIBIOTIC RESISTANCE

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

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  1. ANTIBIOTIC RESISTANCE © 2008 Paul Billiet ODWS

  2. E. Coli Fast breeders • Bacteria reproduce very quickly • Eschericia coli can complete a life cycle in 30 minutes © 2008 Paul Billiet ODWS

  3. 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

  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 • 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

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

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