2.2 Antimicrobial agents Flashcards
antibiotic mechanisms (4)
1 inhibit cell wall synthesis
2 inhibit protein synthesis
3 interferes with DNA synthesis and replication
4 disrupts cell membrane
what antibiotics inhibit cell wall synthesis
beta lactam and glycopeptide
beta lactam antibiotic examples
penicillins, cephalosporins and carbapenems
beta lactams contain a ring of carbons and modifiable residues
have been many generations of cephalosporins
carbapenems are last line antibiotics, main one is meropenem which is broad spectrum
describe beta lactam mode of action
penicillin blocks the active site through penicillin binding protein so the bacteria can’t form the cell wall properly and it breaks open (think of it as punching holes in cell wall)
Inhibiting transpeptidases from linking amino acid side chains.
what are beta lactamase inhibitors and why are they needed
bacteria produce beta lactamases to hydrolyse the beta lactam ring of antibiotic to make it ineffective. So beta lactamase inhibitors block their active site to prevent them destroying the antibiotic, such as clavulanic acid, to leave the antibiotic free to work. E.g. co-amoxiclav= amoxicillin and clavulanic acid
glycopeptide antibiotics examples
vancomycin and teicoplanin, have broad gram positive spectrum
describe glycopeptide mode of action and how resistance occurs
they bind directly to amino acid side chains, so cell wall cross-linking enzymes can’t attach, resistance occurs when bacteria modify side chain structures
give examples of antibiotics that inhibit protein synthesis, will they have an immediate effect?
macrolides, tetracyclines and aminoglycosides
they may not have an immediate effect with bacteria need to constantly turn protein over so blocking this will interfere with growth
example of macrolides
clarithromycin- used to treat community acquired pneumonia
example of tetracyclines
Doxycycline- oral and long lasting, used in COPD
example of aminoglycosides
gentamicin- narrow therapeutic window since can damage kidneys, used for sepsis
give examples of antibiotics that inhibit DNA synthesis and replication
sulphonamides, diaminopyrimidines and quinolones
what do antibiotics that inhibit DNA synthesis and replication exploit
the fact that bacteria have to synthesis folate and cannot absorb it, they interfere with folate synthesis at different stages, use more than one to be more powerful and reduce the chance of resistance (synergistic activity)
what is fluroquinolone and what is it used for
fluorine atom and quinolone, stops DNA unwinding before replication by binding to 2 nuclear enzymes. Causes shredded DNA, rapidly fatal to bacteria
fungi are (p or e)
eukaryotes (have a nucleus)