Mechanisms And Baterial Resistance Flashcards
What does the term “Anti-microbial agents” mean?
Natural substances that are meant to be toxic but are harmless (to the host.
Eg: antibiotics
What does the term “antibiotic mean”?
A natural substance that is taken in small doses to either kill or prevent the growth of bacteria.
What are the four classes of antibiotics?
- spectrum of activity
- Effect on microorganism
- chemical structure
- mode of action
State one advantage and disadvantage of using anti-microbial drugs to fight bacteria.
Adv: anti microbial drugs work against several bacteria’s.
Disadvantage: the drug will also destroy friendly bacteria in the process.
Antibiotics either destroy or slow down the growth of bacterias. Define bactericidal.
Define bacteriostatic.
Bactericidal: irreversible cell death (destroys bacteria)
Bacteriostatic: slows down the growth of bacteria
State the 5 mode of actions.
- Inhibition of cell wall synthesis
- Distribution of cell membrane function
- Inhibition of protein synthesis
- Inhibition of nucleic acid synthesis
- Inhibition of metabolic pathways
Describe the synthesis of the peptidoglycan cell wall
(inhibitors of cell wall synthesis)
Bacteria’s need peptidoglycan for cell wall synthesis.
When the synthesis is inhibited, high osmotic pressure causes the cell to burst.
- The bacteria first increases in size following with binary fission.
- Autolysins then break the glycosidic bonds between the peptidoglycan monomers and the peptide cross bridges.
- New peptidoglycan monomers are then inserted, enabling bacterial growth.
- the penicillin binding proteins then reform the cross link between two layers of peptidoglycan, making the wall stronger.
Describe the steps involved in the “distribution of a cell membrane function”.
- the phospholipid bilateral is disturbed
The antibody then binds to the lipid membrane of the cell, forming pores in the cell membrane, altering the structure - causing the cell to be more permeable which disturbs the osmotic balance and leading ions to leak.
This leads to cell death.
What antimicrobial drugs are involved in the distribution of cell membrane function.
- polymyxins
- nystatin
- amphotericin B
State the antimicrobials that bind to the 30s ribosomal subunit and the side effect.
1 Aminoglycosides: (streptomycin)
- they are bactericidal
- resistance is common
- Tetracyclines
- bacteriostatic
- destruction of normal intestinal flora
- teeth staining/discolouration
State the antimicrobials that bind to the 50s ribosomal subunit.
- Chloramphenicol, clindamycin
(Can be toxic) - Erythromycin
(An alternative to patients allergic to penicillin)
State the antimicrobial drug that inhibits RNA synthesis and the function.
- Rifampicin
- bactericidal
- binds to DNA and inhibits imitation of RNA synthesis
State the antimicrobial drugs that inhibits DNA synthesis and the function.
- Quinolones
- bactericidal
Binds to the A subunit of DNA gyrase and prevents supercoiling of DNA
- used to treat urinary tract infections - Metronidazole
- inhibits anaerobic bacteria and Protozoa
- causes strand to break in DNA
State the function of sulphonamides.
- blocks thymidine and purine synthesis by inhibiting microbial folic acid synthesis
Treats UTIs
State the function of Trimethoprim
- binds to dihydrofolate reductase and inhibits formation of tetrahydrofolic acid
