inhibitors of cell wall synthesis Flashcards
structure conferring cell wall rigidity and resistance to osmotic lysis in both G+ and G- bacteria
peptidoglycan
difference between G+ and G-
- G+: peptidoglycan is the only layered structure external to the cell membrane and it is thick
- G-: outer membrane external to a very thin peptidoglycan
peptidoglycan is composed of a backbone of what two alternating sugars
- N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)
a chain of four amino acids is linked to what sugar in the peptidoglycan
N-acetylmuramic acid (NAM)
a peptide bridge cross links the tetrapeptide chains in the peptidoglycan. Which two amino acids are connected
D-gln and D-ala
inhibition of any stage of the synthesis, export, or assembly of peptidoglycan leads to what
bacterial cell death
how are abx that inhibit cell wall synthesis bactericidal
- cell death due to osmotic lysis
- loss of cell wall integrity is due to bacteria’s autolysins which cleave peptidoglycan bonds in normal course of cell growth
- with abx, autolysis proceeds without normal cell wall repair
name the 4 B-lactams abx
- penicillins
- cephalosporins
- monobactams
- carbapenems
name the 4 natural penicillins. which is the prototype?
- penicillin G
- Benzathine penicillin
- Probaine Penicillin
- Penicillin V
name the 3 penicillins that are penicillinase resistant. which is the prototype?
- Nafcillin
- Dicloxacillin
- Oxacillin
name the penicillins that have extended spectrum. which is the prototype?
- Ampicillin
- Amoxicillin
name the penicillins that are antipseudomonal. which is the prototype?
- piperacillin
- ticarcillin
what is the mechanism of action of penicillins
prevent transpeptidation (cross links pentapeptides of peptidoglycan)
- prevent the action of penicillin binding protein
what group of abx has the highest antibacterial activity against certain G+ bacteria
natural penicillins
coverage of natural penicillins
- Highest coverage against certain G+
- some G- coverage
natural pencillin don’t cover what organisms
- inactivated by B-lactamase (penicillinase): not effective against strains of S. aureus
- No antipseudomonal activity
route of Penicillin G
- IV
- IM
route of Benzathine penicillin
IM
route of Procaine penicillin G
IM
route of Penicillin V
oral
coverage of Penicillinase-Resistant Penicillins
- lower activity against G+
- some G-
what is the DOC for penicillinase producing S. aureus (MSSA)
Penicillinase-resistant penicillins
what group is Nafcillin in
Penicillinase-resistant penicillins
route of administration of Nafcillin
- parenteral
what group is Dicloxacillin (Cloxapen) in
Penicillinase-resistant penicillins
route of administration of Dicloxacillin
oral
what group is Oxacillin in
Penicillinase-resistant penicillins
route of administration of Oxacillin
oral
mechanism of resistance of MRSA
- produces an alternate PBP which decreases affinity of the B-lactam Abx to PBP
what is the only B-lactam that can be used to treat MRSA
Ceftaroline
extended spectrum penicillins have what coverage
- lower G+ coverage
- extended G- coverage
extended spectrum penicillins are ineffective against what organism
no antipseudomonal activity
DOC for Lysteria infections
extended spectrum penicillins
what group is ampicillin in
extended spectrum penicillins
route of administration of extended spectrum penicillins
oral
what group is amoxicillin in
extended spectrum penicillins
what is the ampicillin rash
- occurs in 5-10% of children receiving extended spectrum penicillins
- dull, red, maculopapular rash
- onset: 3-14 after start of Abx
**rash is not allergic
high percentage of patients with what infection will develop a ampicillin rash during therapy with ampicillin
infectious mononucleosis (EBV)
coverage of antipseudomonal penicillins
- extended spectrum penicillins plus some enteric G-
major use of antipseudomonal penicillins
- pseudomonas aeruginosa
- acinetobacter
can antipseudomonal penicillins be used as a seperate abx
NO
- used in combination with aminoglycosides to prevent resistance
what group is Pipercillin in
antipseudomonal penicillins
what group is Ticarcillin in
antipseudomonal penicillins
What are Clavulanic acid, Sulbactam, and Tazobactam
B-lactamase inhibitors
function of B-lactamase inhibitors
- added to ampicillin, amoxicillin, ticarcillin, piperacillin to extend the spectrum to include organisms that are resistant to B-lactamase (penicillinase)
are the penicillins used in combo with B-lactamase inhibitors active against MRSA?
no
Route of administration of ampicillin; sulbactam (Unasyn)
parenteral
route of administration of amoxicillin; clavulanic acid (augmentin)
oral
Route of administration of piperacillin; tazobactam (Zosyn)
IV
route of administration of Ticarcillin; Clavulanic acid (timentin)
IV
different functions of bacterial B-lactamase (penicillinase)
- alteration of PBP
- decreased permeability of bacteria cell to PCN
- autolytic enzymes not being activated -> forming tolerant organisms (bacteria become dormant)
- lack of cell wall
toxicity of penicillins
allergy
abx choice for early infection of borrelia burgdorferi
amoxicillin or doxycycline
