Antibiotics Flashcards
What is selective toxicity
The aim to kill the microbe but not the host
Outline Paul Ehrlich discovery that supported selective toxicity
He noted that some dyes (such as methylene blue) stain microbes better host cells, leading to the idea of a chemical “magic bullet” to kill microbial cells but not the hosts cells.
What was the first selective antibiotic
1909, Salvarsan/compound 606
Outline penicillin
1928 alaxander Fleming observed that colonies of the bacterium staphylococcus bacteria could be destroyed by the mole penicillium notatum (also known as penicillium chrysogenum). This caused a region of inhibition for cell growth around the mole/fungi
How does penicillin work
Interfering with the normal formation of bacterial cell wall by inhibiting the formation of peptide cross bridges.
Bacteria mistake penicillin for amino acid, incorporating it in bacterial all, resulting in leaky cell wall that falls apart.
What targets various bacterial cell components
Various different bacterial cell components are targeted by different classes of antibiotics
What causes antibiotic resistance
Mutations - the most important cause of genetic diversity in microbial populations
What are some causes of mutations
Spontaneous mutations
Environmental causes: Radiation, certain chemicals…
Outline how mutations can select for antibiotic resistance
Antibiotic kills all bacteria, except bacteria displaying antibiotic resistance. Antibiotic resistant bacteria reproduces, all progeny inherit same mutation. All bacteria deriving from single mutated will now be antibiotic. Passed on by horizontal or vertical gene transfer
Outline the enzyme involved in bacterial antibiotic resistance
Beta lactaamase: destroys beta lactation ring of penicillin, rendering antibiotic useless. Is located on a plasmid - can undergo horizontal gene transfer.
Outline plasmids containing antibiotic/resistance genes in bacteria
Plasmids can contain many genes which code for resistance against multiple antibiotics.
Outline vertical gene transfer of antibiotic resistance gene
Proportion of bacteria gains resistance mutation, and these select few survive exposure to antibiotic. Bacteria with resistance then multiply, passing on resistant trait. Resistant bacterial populations survive subsequent encounters with antibiotic.
Outline horizontal gene transfer of antibiotic resistance gene
Some bacteria gene resistance through external source (transformation, transduction, conjugation).
Bacteria with resistance survive antibiotic, and multiply in numbers. Resistant bacterial populations survive subsequent encounters with antibiotic.
Outline the inter/intro specific transmission of antibiotic resistance
Antibiotic resistance can be both intra specific and inter specific
How do you reduce the development of antibiotic resistance
Decrease antibiotic resistance
Improve diagnostics
Identify new targets
Combination of therapies
