Antibiotics Flashcards
What did early treatment for infectious disease such as syphilis involve?
Use of highly toxic medicines more harmful than the actual disease
What did Paul Ehrlich note?
Some dyes (such as methylene blue) stained microbes better than host cells
What did Ehrlich come up with?
The idea of a chemical ‘magic bullet’ to kill microbial cells but not the host cells
What happened in 1909?
The first selective antibiotic Salvarsan or compound 606
What happened in 1982?
Alexander Fleming observed that colonies of the bacterium staphylococcus bacteria could be destroyed by the cold (fungi) penicillium notatum.
What could be seen on the culture of staphylococcus bacteria?
A zone surrounding the fungi where bacterial growth was inhibited
What is the zone of inhibition used for?
To measure antibiotic susceptibility in the Kirby-bauer test
How does penicillin work?
Interfering with the normal formation of the bacterial cell wall by inhibiting the formation of the peptidoglycan cross links
How does the penicillin inhibit formation of peptidoglycan cross links?
Blocks the enzyme which stitches the cell wall together
What are the bacterial cell components targeted by different classes of antibiotics?
- Inhibition of cell wall synthesis
- Inhibition of protein synthesis
- Disruption of cytoplasmic membrane
- Inhibition of general metabolic pathways
- Inhibition of DNA or RNA synthesis
Special Case: Inhibition of pathogen attachment or entry into host cell
What are mutations?
The most important cause of genetic diversity in microbial populations
What happens first in antibiotic resistance?
A proportion of the bacterial population gains resistance to antibiotic X by mutation
What happens after a proportion of the bacterial population gains resistance to antibiotic X by mutation?
Some bacteria with the resistance survive
What happens after some bacteria with the resistance survive?
Bacteria with resistance multiply passing on the resistance trait
What happens after bacteria with resistance multiply passing on the resistance trait?
Resistant bacterial populations survive subsequent encounters with Antibiotic X
What is beta lactamase?
An enzyme produced by bacteria and used to destroy penicillin
How does beta lactamase destroy penicillin?
Breaking a bond in the beta lactic ring to disable the penicillin molecule
What are the types of gene transfer in antibiotic resistance?
Vertical and horizontal gene transfer
What is vertical gene transfer?
From parent to offspring
What is horizontal gene transfer?
From parent to parent
How can we reduce development of antibiotic resistance?
Decrease antibiotic utilisation, improve diagnostics, identify new targets and combination therapies
What is meant by decrease antibiotic utilization?
Reduce infections and outbreaks through improved hygiene and infrastructure, restrict use in agriculture
What is meant by improve diagnostics?
New methods to identify resistant bacteria can make treatment more effective and reduce outbreaks
What is meant by identify new targets?
Some cellular pathways are harder for bacteria to bypass or modify, making them ideal targets for new antibodies
What is meant by combination therapies?
Traditional antibiotics can be combined with molecules that block resistant mechanisms
