Module 10 Flashcards
describe bacteriacidal antibacterial agens
kill microorganisms
immune system responsible for cleaning up cellular fragments
eg. penicillin
describe bacteriostatic antibacterial agents
halt the growth of microorganisms so immune system can elliminate it
immune system must actively be fighting disease or the infection will not resolve
inhibitors of cell wall synthesis
peptidoglycan
- vital component of bacteriual cell wall
- unique to bacteria
- optimum target for selective toxicity
describe penecillin
penicillin V and G, amoxicillin, ampicillin, methicillin, dicloxacillin
prototype for penicillin discovered in 1929, theratpeutic importance and large scale production happened in 1940s
an intact rich structure essentual for antibacterial activity
cleavage of the ring by penicillinases inactivates the drug
mechanisms of action for penicillin
penicillin binds to binding proteins (PBP)
interferes with formation of cell wall
leads to activation of autolytic enzymes –> cell lysis
penicillin is bactericidal, but it kills cells only when bacteria are growing –> active during long phase
disadvantages of penicillins
limited effectiveness against many gram - rods
need frequent doses to be effective
inactived by B-lactamases
cephalosporins
Cefotaxime, ceftriaxone, cefazolin
6 sided ring attached to b-lactam group
first gen cephalosporins active against gram + cocci
2nd/3rd/4th gen cephalosporins active against both Gram +/- bacteria
Gonnorrhea and GBS
resistance and B-lactams
production of B-lactams by staphylococci gram- bacteria, gonocci
over 50 different B-lactamases produced under control of plasmids
Can be specific for one antibiotic or broad spectrum
lack of penicillin receptors or altered PBPs or inaccessibility of receptors bc of permeability barriers of outer membranes
failure of activation enzymes resulted in inhibition w/o killing bacteria
failure to synthesize peptidoglycans = metabolically inactive bacteria that lack cell wall
describe glycopeptides
vancomycin
bactericidal agent
active against gram + bacteria
inhibits the addition of subunits to cell wall
agents act an earlier stage then B-lactams
–> not useful in combination
–> slow killers than B-lactams
used to treat MRSA and Clostridium difficile
Inhibitors of protein synthesis
inhibit synthesis w/o interfering with synthesis in human cells
selective toxicity due to differences in bacterial and human ribosomes
describe aminoglycosides
a family of moelcules with bactericidal activity
streptomycin
neomycin
gentamicin
mechanisms of action aminoglycosides
binding to specific proteins in subunit
–> inhibit the initiation complex –> important for bactericidal activity of the drug
misreading of mRNA results in inhibition of initiation and misreading
membrane damage occurs and bacterium dies
given intravenously or intramuscularly
administered to women with PROM and babies with suspected sepsis
production of aminoglycoside-modifying enzymes –> most important mechanism of resistance
GENTAMICIN NOT FOR PREGNANCY
describe tetracycline
tetracycline, doxycycline
inhibit the binding of tRNA to the ribosome –> prevent protein synthesis
bacteriostatic action
administered orally
doxycycline is completely absorbed
used to treat chlamydia and mycoplama
describe tetracycline resistance
bacteria make new cytoplasmic membrane proteins capable of pumping tetracycline out of resistant cells
side effects of tetracycline side effects
should be avoided in pregnancy and children under 8
result in permanent teeth staining
photosensitive allergic reaction increases the risk of sunburn
supress normal gut flora
superinfection can occur
pseudomembranous colitis
macrolides
erythromycin, azithromycin, clarithromycin
prevents the release of tRNA after peptide formation
bacteriostatic
useful in STI treatment during pregnancy when tetracyclines contradicted
macrolides resistance
plasmid-encoded genes
active pump mechanisms for efflux of macrolides
can protect the ribosome from actin of macrolides by production of methylase enzymes that alter the binding site
describe erythromycin
active against gram-positive cocci
alternative treatment to streptococcus in patients allergic to penicillin
active against chlamydia and mycoplasma
given prolonged ROM in membranes in penicillin allergic clients
good against gram+ microbes (GBS)
given orally/IV
azithromycin
azithromycin penetrates into most tissues (not CSF)
slowly released which permits once daily dosing and shortening of the duration of treatment in many cases
a single 1g dose is as effective as a 7 day course of doxycycline for chlamydial cervicitis and urethritis
describe lincosamides: clindamycin
inhibits peptide formation
primarily active against aerobic gram+ bacteria and anaerobic bacteria
active against chlamydia, gonnorrhoea, GBS and BV
used vaginally in the treatment of women with BV in pregnancy
describe quinolones
Nalidixic acid, ciprofloxacin, OFloxacin
synthetic, bactericidal agents
inhibit bacterial DNA gyrase –> ensures DNA has proper conformation for efficient replication
when inhibited, DNA gets twisted and is unreadable
able to interfere with this enzyme in bacteria without affecting it in humans (do not have DNA gyrase)
effective against Gram -
2nd/3rd gen can target some gram +
administered orally
used to treat UTI, chlamydia and gonorrhea
NOT FOR CHILDREN, PREGNANT OR LACTATING WOMEN
describe quinolone resistance
Chromosomally mediated
change in target enzymes –> affect quinolone binding
change in cell wall permeability –> decrease uptake
describe folic acid synthesis inhibition
synthetic bacteriostatic agents
have a specttrum of activity primarily against gram -
inhibit bacterial metabolic pathways which produce precursors for nucleic acid synthesis
describe sulfoamides
compete with PABA for active site on enzyme that catalyzes essential run in pathways producing NA precursors
THFA is the biologically active form of folic acid –> cant make folic acid =die
selective toxicity –> bacteria make their own folic acid, drug does not impact human pathway
administered orally
treats UTIs
widespread resistance
avoided in 1st tri due to impact on folic acid
not used near end of pregnancy due to impact on bilirubin
