Transcript Antibiotics
Antibiotics Noadswood Science, 2011 Friday, April 8, 2016 Antibiotics To understand how antibiotics work and the advantages and disadvantages associated with them Antibiotics Antibiotics are substances that kill bacteria or stop their growth (often targeting the bacteria’s cell capsule) They do not work against viruses – it is difficult to develop drugs that kill viruses without also damaging the body’s tissues Antibiotics Antibiotic Target Penicillin Breaks down cell walls Erythromycin Inhibits protein synthesis Neomycin Inhibits protein synthesis Vancomycin Inhibits protein synthesis Ciprofloxacin Inhibits DNA replication Penicillin The first antibiotic (penicillin) was discovered in 1928 by Alexander Fleming He noticed that some bacteria he had left in a petri dish had been killed by naturally occurring penicillium mould Since the discovery of penicillin, many other antibiotics have been discovered or developed – most antibiotics used in medicine have been altered chemically to make them more effective and safer for humans Resistance Bacterial strains can develop resistance to antibiotics, due to natural selection In a large population of bacteria, there may be some cells that are not affected by the antibiotic – these cells survive and reproduce, producing even more bacteria that are not affected by the antibiotic MRSA (methicillin-resistant staphylococcus aureus) – it is very dangerous because it is resistant to most antibiotics It is important to avoid over-use of antibiotics, so we can slow down, or stop, the development of other strains of resistant bacteria Resistance Although vaccinations and antibiotics are useful in the fight against pathogens, bacteria and virii can mutate to form a new resistant ‘strains’... Bacteria 1. Variation – some strains of bacteria are resistant 2. Competition – the non-resistant bacteria are killed by the penicillin 3. Survival of the fittest – the resistant bacteria survive Antibiotic 4. Reproduction – the resistant bacteria reproduce and pass on their adaptations to their offspring Bacterial Growth Using the agar plates spread bacteria evenly over them Place some antibiotic disks randomly onto the culture (ensure you note which antibiotic plate is which)! Which antibiotic is the best? A Which antibiotic are the bacteria most resistant to? B C D E Bacterial Growth Using discs on agar covered with bacteria – this technique is used in hospitals on samples of urine, blood and stools to work out which antibiotic to use The antibiotic disc which has the caused the widest circle in the bacterial plate is the best for that type of bacteria – it has killed the highest quantity of bacteria (C) A B C D E The antibiotic which the bacteria are most resistant too has the smallest circle (B) Cleanliness One simple way to reduce the risk of infection is to maintain personal hygiene and to keep hospitals clean In the 19th century Semmelweis realised the importance of cleanliness in hospitals – however, although his ideas were successful, they were ignored at the time because people did not know that diseases were caused by pathogens that could be killed MRSA – Research How can we control the spread of antibiotic resistant bacteria in hospitals? Could we stop using antibiotics – why / why not? Defence