Anti-microbial Flashcards
Define chemotherapy
Use of drugs (chemicals) to treat a disease
Define antimicrobial drugs
E.g. penicillin
A chemical that interferes with growth (kills or inhibits) of microorganism within a host
Define antibiotic
Of biological origin. Chemical produced by microorganism, that kills or inhibits the growth of another microorganism.
Define chemotherapeutic agent?
Synthetic chemicals
Define selective toxicity
A drug that kills harmful microbes without harming the host
Many newer antibiotics are biological products that are…
Chemically modified or chemically synthesised
What are the 2 main families of bacteria?
Gram +
-has 1 cell membrane
-e.g. staphylococcus aureus
-peptidoglycan (protein chain, with sugar molecules) is exposed + takes
up gram stain
-e.g. bacilli (e.g. aerobic =listeria or anaerobic =clostridium) + cocci (e.g.
staphylococci)
Gram -
- has 2 cell membranes
- peptidoglycan is hidden between membranes, so the gram stain can’t get to it, can’t penetrate cell membrane
- e.g. E. coli, diplococci, coccobacilli
- use lactose fermentation (lactose for energy)
History of chemotherapy…. name 2 drugs developed in 1900s
-Salvarsan (arsphenamine) has arsenic in it, toxic. Developed
against syphillis
-sulphurdrugs (sulphonamide) discovered against gram +bacteria (now
used for UTIs)
Whats the difference between bacteriostatic + bactericidal
Bacteriostatic = stops bacteria reproducing (inhibits bacterial growth)
Bactericidal = actively kills bacteria (e.g. used when treating immunosuppressant pts)
What is the tissue distribution, metabolism + excretion factors of bacteria?
-BBB?
-unstable in acid? (some have to be injected)
-half-life duration? (Often have to take QDS e.g. flucloxacillin, half life
30min)
What are the features of BZs?
- broad spectrum (kills of several species)
- short half-life (30min)
- crosses BBB (used in meningitis)
- bactericidal
- unstable in acid (given IV)
What is the 5 actions of antimicrobial drugs?
- Inhibition of cell wall synthesis e.g. penicillins, cephalosporins
(e.g. cefadroxil, used for UTIs) + vancomycin (last resort, still
some resistance to it, used for septicaemia or endocarditis) - Inhibition of protein synthesis e.g. erythromycin
- Inhibition of nucleic acid replication + transcription e.g. rifampin + quinolones (GABA antagonists)
- Injury to plasma membrane e.g. polymyxin B (problem is that ALL
organisms have one = more likely to affect host). - Inhibition of synthesised of essential metabolites e.g. sulfanilamide
(don’t affect cell wall, just kill of bacteria by paralysing enzymes).
Give an example of drugs that inhibits protein synthesis
Chloramphenicol
- given as eye drops for bacterial conjunctivitis
- wide spectrum
Aminoglycosides
- e.g. gentamicin
- causes non functional proteins to be synthesised
- bactericidal
- narrow therapeutic index + toxicity
- streptomycin used for TB, replaced with rifampicin
Tetracycline
- causes non functional proteins to be synthesised
- used for chlamydia
Macrolides
- e.g. erythromycin
- don’t penetrate BBB - can’t be used to treat meningitis
What’s a beta-lactam antibiotic?
-have a beta lactam ring in their structure
-unstable ring - if there’s a change in shape the molecule falls
apart + doesn’t function. Penicillin mimics an enzyme bacteria needs to
produce its cell wall. The bacteria picks it up, penicillin breaks down =
bacteria can’t synthesis or repair cell wall.
-e.g. penicillin + cephalosporin
-bacteria produce an enzyme called beta lactamase (resistant strains) which breaks down the lactic ring = destroys the antibiotic
What antibiotic is effective against beta-lactamase?
Flucloxacillin, producing staphylococci
The enzyme augmentin destroys beta lactamase (contains penicillin + anti beta lactamase)
