Antimicrobial Chemotherapy

three mechanisms of action of antibiotics

inhibition of ______ synthesis

cell wall, protein, nucleic acid

antibiotic cell wall synthesis inhibitors for gram positive organisms

penicillin, cephalosporins (B lactams) and glycopeptides

glycopeptide antibiotic example

vancomycin (toxic)

which act first B-lactams or glycopeptides?

glycopeptides act on proteins that link sugar strands so they can't be cross-linked

B-lactams stop the PBP from binding the proteins

reason protein synthesis can be targeted by antibacteria

different ribosomes present in eukaryotic and prokaryotic cells

protein synthesis inhibitors for gram negative organisms

aminoglycosides

aminoglycoside antibiotic example

gentamicin

cheapest commonly used but toxic

protein synthesis inhibitors for gram positive infections

macrolides, tetracyclines, oxazolidinones, cyclic lipopeptides

macrolide antibiotic example and when useful

erythromycin for penicillin allergic patients

oxazolidinones antibiotic example and when used

linezolid used when bacteria is resistant to other options

cyclic lipopeptide antibiotic example

daptomycin

not common only for very resistant bacteria

antibiotic inhibitors of nucleic acid synthesis

purine synthesis inhibitors, fluoroquinolones (particularly effective against gram negative)

two antibiotics involved in inhibiting purine synthesis

trimethoprim (used against UTI and chest infections) and sulphamethoxazole

Ciprofloxacin (fluoroquinolone)

cannot be used in children

two ways to combat B-lactamase

modify the penicillin so it can't be degraded by enzymes (flucloxacillin)

give antibiotic with B-lactamase inhibitor (clavulanic acid)

polyenes anti-fungal drug

bind to ergosterol in fungal cell membrane

azole anti-fungal drug

inhibit ergosterol synthesis in yeast infections

allylamines anti-fungal drug

supress ergosterol synthesis but different stage than azoles

only allylamine used

terbinafine

echinocandins anti-fungal drug

inhibit synthesis of glucan polysaccharide

MIC

minimum concentration of anitmicrobial needed to inhibit visible growth of a given organism

MBC

minimum concentration of antimicrobial needed to kill a given organism

sensitive/resistant

orgnanism is/isn’t inhibited or killed by levels of the antimicrobial that are available at the site of infection.

bactericidal example

penicillins