Antibiotics Flashcards
What is selective toxicity?
Choosing treatments that selectively choose pathogens and not other body cells, in order to kill the disease, not the patient
How was selective toxicity invented?
Paul Ehrlich noted that some dyes (such as methylene blue) stained better then host cells
How was Penicillin found?
In 1928 Alexander Fleming observed that colonies of the bacterium Staphylococcus bacteria could be destroyed by the mold Penicillium notatum
What is the zone of inhabition?
Where bacterial growth is inhibited (used to measure antibiotic susceptibility)
What is Penicillin effective against?
Particularly effective against gram positive, still effective against gram negative
How does Penicillin affect bacteria?
Interfering with the normal formation of the bacterial cell wall by inhibiting the formation of peptidoglycan cross-links
- Cuts the sugar links and stops the cross-links from being formed
What are the different bacterial components that are targeted by antibiotics?
Inhibition of cell wall synthesis (penicillin)
Inhibition of protein synthesis
Disruption of cytoplasmic membrane
Inhibition of general metabolic pathway
Inhibition of DNA or RNA synthesis
Inhibition of pathogens attachment or entry into host cells
Why does antibiotic resistance occur?
The pressure on bacterial populations because of penicillin and other antibiotics caused bacteria to select for those who could survive them
- Mutations are the most important cause of genetic diversity in microbial populations that cause them to gain resistance
How does vertical gene transfer occur, in the context of bacterial resistance?
- A proportion of the bacterial population can gain resistance to a specific antibiotic by mutation (denovo)
- Bacteria with this resistance can multiply, passing on the trait
- This resistant bacterial population survive subsequent encounters with antibiotic x
(All children will have the resistance gene from and resistance parent)
What is Beta lactamase?
An enzyme produced by bacteria and used to destroy penicillin
Chops up the beta lactam ring
What is horizontal gene transfer?
Some bacteria gain resistance by acquiring gene from external sources, this can occur through: Transformation, tranduction, conjugation
How do we reduce the development of antibiotic resistance?
Decrease antibiotic utilization (reducing pressure on anti bacterial populations)
Improve diagnostics (viruses are not affected by antibiotics, make sure that only the people that need them are getting them - only bacteria)
Identify new targets (no one is making new antibiotics anymore)
Combination therapies (antibiotics can be combined together - less likely to have bacterial resistance)
