Anti-microbial Chemotherapy Flashcards
What is MIC
the minimal inhibitory concentration is defined as the minimum concentration of antimicrobial needed to inhibit visible growth of a given organism
What is MBC
the minimal bactericidal concentration is defined as the minimum concentration of antimicrobial of the antimicrobial needed to kill the given organism
What does it mean for an organism to be sensitive
If it is inhibited or killed by levels of the antimicrobial that are available at the site of action
what does it mean for an organism to be resistant
If it is not killed or inhibited by levels of the antimicrobial that are available at the site of the infection
What is a Bactericidal
an antimicrobial that kills bacteria
What is a Bacteriostatic
An antimicrobial that inhibits growth of bacteria
The mechanism of action of antibacterial drugs
inhibition of cell wall synthesis
inhibition of protein synthesis
Inhibition of nucleic acid synthesis
Inhibition of cell wall synthesis
Penicillins and cephalosporins - contail B-lactams, inhibit enzymes responsible for cross-linking carbohydrates to form peptidoglycan chains
Glycopeptides - vancomycin and teicoplanin, act on stage prior to when B-lactams act, inhibiting the production os peptidogylcan precursor, only act on gram +ve bacteria
Inhibition of Protein synthesis
Aminoglycosudes- gentamicin, mainly used to treat Gram -ve infections
macrolides and tetracyclines - erythromycine, clarithromycin, used in gram +ve infections, mainly used to treat haemophilus influenza
Oxazolidinones - linezolid, used against MRSA
inhibition of nucleic acid synthesis
trimethoprim and sulphamethoxazole - inhibit different steps in purine synthesis, ised in combined form, co-trimoxazole for chest infections, trimwethoprim for UTI’s
Fluoroquinolones - ciprofloxacin, inhibit DNA synthesis more directly, effective against gram -ve infection, cannot be used in children due to danger of cartilage growth interference
the mechanism of action for antifungal drugs
polyenes, azoles, allylamines, echinocandins
action of polyenes
bind to erosterol and make cell wall more permeable
amphoyericin B is used to treat serious fungal and yeast infections but is toxic
nystatin is used topically or in oral suspension
action of azoles
inhibit ergosterol synthesis
fluconazole is used to treat yeast infections, but not all are sensitive
voriconazole and itraconazole used to treat aspergilliosis
action of allylamines
suprerss ergosterol synthesis but at a differet stage than azoles
terbinafine is the only one in use
mainly used against deratophytes and clinical use is restricted to infection of skin and nail
action of echinocandins
inhibit the production of glucan ploysaccharide
casofungin is used in serious candida and aspergillus infection
it is a safe, IV only drug