ANTIBIOTIC RESISTANCE

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

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

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

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)

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

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

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

Antibiotic use and abuse Viral infections are not stopped by antibiotics