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Antibiotics and bacterial resistance

AS Biology Unit 2

Jane Hampson

on 25 March 2014

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Transcript of Antibiotics and bacterial resistance

Streptomycin (and other aminoglycoside antibiotics) are bacteriostatic. They bind to ribosomes and interfere with protein synthesis. This inhibits the growth of the bacteria.
How can this inhibition help a patient with an infection to recover?
Why do these drugs not damage the patient's own body cells?
These drugs interfere with the synthesis of bacterial cell walls.
When bacteria grow, they add new sections to their outer cell wall. This involves the actions of enzymes to make and break bonds in the peptidoglycan polymers. Penicillin is a competitive inhibitor of one of these enzymes. The cell wall is weakened and the bacterial cells eventually burst due to osmotic lysis.
Antibiotics are drugs which can be used to treat bacterial infections. They selectively interfere with bacterial metabolism.
How is this possible?
There are two main types of antibiotics:
bacteriostatic drugs, like streptomycin:
these inhibit the growth of bacteria but do not kill them.
bactericidal drugs, like penicillin:
these kill bacteria sensitive to them.
Bacteria are single cells and do not have an immune system. They can develop resistance to antibiotics by mutation.
Which genes would you expect to be involved in developing resistance to
Vertical transmission
When bacteria grow and make new cells, their DNA is replicated. Mutations will therefore be passed to all the descendants of the original mutant from a population.
Drug resistance in clinical situations.
In many hospitals, strains of multiple drug resistant bacteria are frequently isolated. These present an enormous problem.
What are the challenges for treatment of patients?
Why do strains of bacteria occur in these places with resistance to many different antibiotics?
What do you think should be done to prevent the spread of these resistant bacteria?
Antibiotics and bacterial resistance
Horizontal transmission
Many bacteria have small circular DNA molecules called plasmids. The genes for antibiotic resistance are often present on these molecules. These can be copied and passed to other bacterial cells of the same species and even of different species, in a process called CONJUGATION
The image show the effect of different antibiotic-soaked disks on a 'lawn' of two different bacteria. Explain what has happened and compare the two plates.
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