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FUN 24 ANTIBIOTICS - CELL WALL INHIBITORS (cephalosporins (5 generations…
FUN 24 ANTIBIOTICS - CELL WALL INHIBITORS
2 classes
B-lactams
4 member ring
4 subtypes
penicillins
cephalosporins
carbapenems
monobactams
low toxicity
adverse effects:
diarrhoea
seizures
penicillin allergy
Glycopeptides
Pencillins
4 subtypes
standard penicillins
from penicillium notatum
for syphilis, streptococci, meningococci
penicillin G - IV
Penicillin V - oral
anti-staphylococcal penicillins
not B-lactamase substrates :)
main agent = methicillin
MRSA resistant to this :(
mutated penicillin binding protein 2a due to gene mecA
amino penicillins
good for gram -ve - influenza, E Coli, salmonella
ineffective for staph
anti-pseudomonal penicillins
carboxypenicillins = ureidopenicllins
enhanced activity against pseudomonas aeruginosa
MOA
ala-ala (transpeptidase substrate) mimetic
irreversibly binds to transpeptidase + inhibits it
no cell wall cross linking
lipoteichoic acid (autolysin inhibitor) leaks
lysis
cephalosporins
isolated from mould
same MOA as penicillins
5 generations
gram -ve activity increases
staphylococcal activity decreases
B-lactamase resistant
:( - degraded by cephalosporinase (type 1 chromosomal B-lactamse)
B-lactamase inhibitors
NO ANTIMICROBIAL ACTIVITY
combination therapy with B-lactams
binds covalently to B-lactamase, NOT cephalosporinase
glycopeptides
e.g. Vancomycin
made by streptomyces orientalis
large - IV
for gram +ve + MRSA
! resistance
VanR + VanS sense drug
VanH converts pyruvate to lactate
VanX cleaves ala-ala
VanA/B makes ala-lactate
binds to transpeptidase but not vancomycin
cell wall thickens
bind to ala-ala
resistance mostly in enterococci + staph
! species transfer