antibiotics (pharmacology) Flashcards
what do antibiotics do
they attack the cells that have infected our body/ tissues, they do not attack out own cells. they target cells that have taken over the body
what are the main groups of antibiotics
- sulphonamides
- penicillins
- cephalosproins
- carbipenems
- monobactams
- tertracyclines
- aminoglycosides
- macrolides
- fluroquinolones
define spectrum
- narrow spectrum antibiotic
- effective against only specific families of bacteria - broad spectrum antibiotic
- active against a wide range of disease-causing bacteria
define bacteriocidal
treatment of bacterium so that the organism is killed e.g. heat, filtration, radiation and exposure to chemicals
define bacteriostatic
treatment that restricts the ability of the bacterium to grow e.g. refrigeration, freezing
what are the structural differences between bacterial cells (prokaryotic) and human cells (eukaryotic)
- prokaryotes have no nucleus
- they have an additional cell wall
- their cell membrane is similar to our own but it has no sterols e.g. cholesterol
- it has a single chromosome loose in cytoplasm
- they have no mitochondria
how do antibiotics target bacterial cells
- folate metabolism
- folic acid is needed by both humans and bacteria for DNA and RNA synthesis
- unlike humans, bacteria can not absorb folic acid from food so they have to make it for themselves
- this can be exploited by some antibiotics to inhibit DNA/ RNA production - protein synthesis
- there are some differences between bacterial and mammalian cytoplasmic ribosome that makes them good targets for ‘selective toxicity’
- however, mammaliam mitochondrial ribosomes more closely resemble bacterial ribosomes and high levels of these agents may cause toxic effects as a result of interaction with mitochondrial ribosomes - sulphonamides
- prontosil (a type of dye) was activated within the body to give sulphanilamide which could alter the course of bacterial infection - cell wall
- the bacteria cell wall is made of peptidoglycan which encloses the bacteria and cell membrane
- the antibiotics target the cell wall and those layers, the change in osmotic pressure will cause the water from outside the cell to flow into the cell until it expands and pops
unwanted side effects of sulphonamides (alter the course of bacterial infection)
- nausea and vomiting
- headache, mental depression
- hypersensitivity reactions
- hepatitis
- bone marrow depression
how does penicillin target the cell wall
-peptidoglycan that the bacteria cell wall is made from is heavily cross linked. the enzymes involved in the formation of these cross-links are called transpeptidases. It is these enzymes that penicillin binds to. By inhibiting the formation of the cross links, penicillins weaken the cell wall. this allows water from outside the cell to go inside the cell, changing the osmotic pressure and the cell expands from the water until it pops and dies
cell target wall- teixobactin
- kills bacteria by causing their cell walls to break down
- attacks many other growth processes at the same time, meaning bacteria are unable to quickly develop resistance to the antibiotic
what type of antibiotic is penicillin
- it is a beta-lactam antibiotic
- betalactamase enzymes are produced by some bacteria and can open the B- lactam ring of the antibiotic rendering it ineffective
what are the antibiotics that target the cell wall
- penicillin
- cephalosporins
- monobactams
- carbapenema
- vancomycin
- teixobactin
how does vancomycin and teicoplanin target cell walls
- they inhibit bacterial cell wall synthesis at a site earlier than that inhibited by beta-lactam antibiotics
how does cephalosporins and cephamycins target cell walls
- their molecular structure is closely related to that of the penicilins and its mode of action is that all of the beta lactams- they inhibit cell wall synthesis via disruption of transpeptidase enzymes
