Penicillin Flashcards
(60 cards)
what structure confers cell wall rigidity and resistance to osmotic lysis in both G+ and G- bacteria?
peptidoglycans - large sacculus that surrounds bacterium
- In G+, peptidoglycan is only structure external to cell membrane
- In G-, there is an outer membrane external to thin peptidoglycan layer
what are peptidoglycans composed of?
- backbones of two alternating sugars
- chain of 4 amino acids
- peptide bridge that cross links the tetra peptide chains
“inhibition of any stage of synthesis/export/assembly of peptidoglycan leads to inhibition of bacterial cell growth and, in most cases, _____________”
“inhibition of any stage of synthesis/export/assembly of peptidoglycan leads to inhibition of bacterial cell growth and, in most cases, CELL DEATH”
how are peptidoglycans formed?
- addition of subunits, assembled in cytoplasm
- transport through cytoplasmic membrane to cell surface
- subsequent cross-linking by cleavage of terminal stem-peptide amino acid
when can antibiotics interfere with cell wall synthesis of the peptidoglycans?
- transglycosylation (joining NAM-NAG)
- transpeptidation (cross links pentapeptides)
- NAG reduction to NAM
- transport across the inner membrane
- amino acid mimicry (pentapeptide chain)
***for #1, #2 - enzymatic action performed by PENICILLIN BINDING PROTEINS (PBPs)
what does fosfomycin do?
inhibits one of the first steps in synthesis of peptidoglycan
what does cycloserine do?
structural analog of amino acid D-alanine, needed in synthesis of peptidoglycan
what does bacitracin do?
inhibits conversion to its active form of lipid carrier that moves water soluble cytoplasmic peptidoglycan subunits through cell membrane to cell exterior
what do glycopeptides (vancomycin) do?
sterically inhibit addition of subunits to peptidoglycan backbone
what do beta-lactam antibiotics (penicillins, cephalosporins, carbapenems, monobactams) do?
prevent cross linking reaction called transpeptidation
- performed by transpeptidases or PBPs
are antibiotics that inhibit bacterial cell wall synthesis bacteriostatic or bactericidal?
virtually all = bactericidal
w/ antibiotics that inhibit cell wall synthesis, why do cells die?
osmotic lysis
why do cells have loss of cell wall integrity following treatment?
autolysins
w/ agents that inhibit cell wall growth, ________ proceeds without normal cell wall repair.
w/ agents that inhibit cell wall growth, AUTOLYSIS proceeds without normal cell wall repair.
protein synthesis inhibitors _________ the action of the cell wall synthesis inhibitors
protein synthesis inhibitors PREVENT the action of the cell wall synthesis inhibitors
what are properties of ICWS?
properties of ICWS:
- activity against G+
- spectrum (G-, anaerobic, etc coverage)
- activity against Pseudomonas aeruginosa
- acid resistance - oral absorption
- CNS penetration
- route of elimination
- uniwue adverse effects
list: Beta lactams
- penicillins
- cephalosporins
- monobactams
- carbapenems
list: other inhibitors of CWS (not beta lactams)
- vancomycin
- fosfomycin
- bacitracin
- cycloserine
list: penicillins –> natural penicillins
- PENICILLIN G (prototype)
- benzathine penicillin
- procaine penicillin G
- penicillin V
list: penicillins –> penicillinase
- NAFCILLIN (prototype)
- docloxacillin
- oxacillin
- *Methicillin
list: penicillins –> extended spectrum
- AMPILLIN (prototype)
- amoxicillin
- bacamicillin
list: penicillins –> antipseudomonal
- PIPERACILLIN (prototype)
- ticarcillin
- mezlocillin
- carbeicillin
info about NATURAL PENICILLINS
- HIGHEST antibacterial activity against certain G+ bacteria, incl. G+ anaerobic bacteria
- some G- coverage
- readily activated by BETA LACTAMASE (penicillinase), not effective against strains S. aureus
- NO ANTIPSEUDOMONAL activity
- eliminated by kidney
- poor CNS penetration
- Pencillin V acid resistant
how can the natural pencillins be administered?
PEN G = IV, IM
benathine penicillin = IM depot
procaine penicillin = IM
pen V = oral
