ANTIBIOTIC RESISTANCE © 2008 Paul Billiet ODWSODWS

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

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 ODWSODWS

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 ODWSODWS

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 ODWSODWS

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 ODWSODWS

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 ODWSODWS

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 ODWSODWS

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 ODWSODWS

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 ODWSODWS