Penicillins Flashcards
How does fosfomycin inhibit cell wall synthesis?
Fosfomycin prevents the reduction of NAG to NAM and prevents transglycosylation. It stops one of the first steps in peptidoglycan synthesis
5 points antibiotics can target peptidoglycan synthesis:
- Transglycosylation
- Transpeptidation
- NAG-NAM reduction
- AA mimicry
- Transportation out of the cell
How does cycloserine inhibit cell wall synthesis?
Cycloserine is a structural analog of D-ala (part of the pentapeptide chain)
What part of peptidoglycan synthesis does bacitracin inhibit?
Bacitracin interferes with the transportation of the peptidoglycan subunits across the inner cell membrane
How do glycoproteins such as vancomycin inhibit cell wall synthesis?
Vancomycin sterically inhibits the addition of subunits to the NAG/NAM backbone
What are the four classes of penicillins?
Natural penicillins, penicillinase resistant penicillins, extended spectrum penicillins, antipseudomonal penicillins
What ICWS antibiotics are beta-lactams?
Penicillins, cephalosporins, monobactams, carbapenems
What other drugs (non beta lactams) are ICWS?
Cycloserine, vancomycin, fosfomycin, and bacitracin
What are the natural penicillins and their mode of administration?
- Penicillin G - IV,IM, PO?
- Benzathine penicillin - IM
- Procaine Penicillin G - IM
- Penicillin V - PO (acid resistant)
List the penicillinase resistant penicillins and their mode of administration?
- Nafcillin - IV, IM
- Oxacillin - PO
- Dicloxacillin - PO
- Methicillin -testing only!
List the extended spectrum penicillins and the mode of administration
- Ampicillin - PO
- Amoxicillin - PO
- Bacampicillin
Characteristics of natural penicillins:
- Best G+ coverage (includes anaerobes)
- Some G- coverage
- Inactivated by penicillinase
- Not antipseudomonal
- Renal excretion
- Poor CNS penetration
Characteristics of penicillinase resistant penicillins:
- Less G+ coverage
- Some G- coverage
- Resistant to penicillinase
- Not antipseudomonal
- Some are acid resistant
- Liver metabolism and renal excretion
- DOC-penicillin resistant staphylococcus aureus (MSSA)
- -> 20% will also be methicillin resistant
Characteristics of the extended spectrum penicillins:
- Lower G+ activity
- Extended G- activity
- Not antipseudomonal
- Inhibited by penicillinase
- Urinary excretion
- Acid resistant
- DOC- lysteria infections
* **ampicillin rash is not an allergic reaction. No need to stop the antibiotic
Characteristics of antipseudomonal penicillins:
- Similar coverage to extended spectrum penicillins
- Most often used for pseudomonas aeruginosa and acetinobacter infections
- Often used in combination with aminoglycosides
- Tend to be acid sensitive
- Renal excretion
- Penicillinase sensitive
List the three penicillinase inhibitors:
Clavulonic acid, sulbactam and tazobactam
Penicillins can have an extended spectrum with the addition of a penicillinase inhibitor. What are these combos and their methods of administration?
- Ampicillin + sulbactam (IV/IM)
- Amoxicillin + clavulonic acid (PO)
- Piperacillin + tazobactam (IV)
- Ticarcillin + clavulonic acid (IV)
How can bacteria develop resistance to penicillins?
- Production of beta-lactamase
- Alter the PBP (target of penicillins)
- Decrease permeability of the membrane
- Autolytic enzymes not activated
- Lack of a cell wall
where are PBPs located? and where are beta lactamases located if they are present
PBPs are located in they cytoplasmic membrane while beta-lactamases are located in the periplasmic space
what is peptidoglycan composed of?
- backbone of alternating sugars (NAG and NAM)
- pentapeptide chain
- crossbridge (D-gln and D-ala)
MRSA mechanism of resistance
not due to beta lactamase therefore penicillinase resistant antibiotics are not effective. they change the PBP to a version that most penicillins are incapable of binding to. they alter it to PBP2a
Toxicity due to penicillin:
- allergic reaction
- electrolyte imbalance
- GI disturbance
- superinfections
what does probenecid do?
it decreases renal excretion
Helicobacter pylori treatment:
bismuth+metrondiazole+tetracycline or amoxacillin
