antibiotic resistance © 2008 paul billiet odwsodws

ANTIBIOTIC RESISTANCE

© 2008 Paul Billiet ODWS

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


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 © 2008 Paul Billiet ODWS

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 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


Antibiotic use and abuse Viral infections are not stopped by

antibiotics Yet doctors still prescribe (or are coerced

into prescribing) antibiotics to treat them


antibiotic resistance © 2008 paul billiet odwsodws

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