ICWS I Flashcards
What is the primary goal of understanding antibiotics?
To understand the use of antibiotics
This includes their mechanism of action, spectrum of activity, and adverse effects.
What major difference exists between bacterial and mammalian cells?
The presence of a rigid cell wall external to the cell membrane
The cell wall protects bacterial cells from osmotic rupture.
What is the structure that confers cell wall rigidity in bacteria?
Peptidoglycan
Peptidoglycan is a large, covalently linked sacculus that surrounds the bacterium.
What are the two alternating sugars in the peptidoglycan backbone?
N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG)
These sugars form the structural backbone of peptidoglycan.
What are the points where antibiotics can target to interfere with cell wall synthesis?
- Transglycosylation
- Transpeptidation
- NAG reduction to NAM
- Transport across the inner membrane
- Amino acid mimicry (D-ala)–pentapeptide chain
These processes are crucial for the synthesis of peptidoglycan.
What is the role of penicillin binding proteins (PBPs)?
PBPs are the target of all beta-lactam antibiotics
Inhibition of PBPs leads to cell lysis.
What happens when any stage of peptidoglycan synthesis is inhibited?
It leads to inhibition of bacterial cell growth and often cell death
This is due to osmotic lysis.
True or False: Most inhibitors of cell wall synthesis are bactericidal.
True
These inhibitors lead to the loss of cell wall integrity.
What is the consequence of the action of protein synthesis inhibitors on autolysins?
They prevent the synthesis and action of autolysins
This leads to antagonism of inhibitors of cell wall synthesis.
What are the classes of beta-lactams?
- Penicillins
- Cephalosporins
- Monobactams
- Carbapenems
These are the main classes of beta-lactam antibiotics.
Which part of the beta-lactam structure is crucial for antibacterial activity?
Beta-lactam ring
The integrity of this ring is essential for the drug’s action.
What is penicillinase?
An enzyme that hydrolyzes the beta-lactam ring and inactivates penicillin
This is a method of bacterial resistance.
What is the pharmacokinetic characteristic of Penicillin V?
Oral absorption is adequate with food
It can be taken on an empty stomach.
What is the drug of choice (DOC) for syphilis?
Benzathine penicillin
It is administered intramuscularly and has a long-acting effect.
What is the mechanism of resistance for MSSA?
Production of β-lactamase which hydrolyzes the beta-lactam ring
This inactivates the antibiotic.
What distinguishes MRSA from MSSA in terms of resistance?
MRSA produces a mutant form of PBP which decreases the affinity of β-lactams
No β-lactam can be used to treat MRSA, except ceftaroline.
What are extended spectrum penicillins effective against?
- E. coli
- Salmonella
- Shigella
- H. influenzae
- Proteus
They have lower G+ coverage but extended G- coverage.
What is the significance of adding β-lactamase inhibitors to beta-lactam antibiotics?
It extends the spectrum of these drugs to include organisms resistant due to β-lactamase production
Examples include clavulanic acid, sulbactam, and tazobactam.
Fill in the blank: The addition of ________ to amoxicillin can restore its antibacterial activity against β-lactamase producing bacteria.
beta-lactamase inhibitors
This combination allows amoxicillin to remain effective against resistant strains.
What is the role of β-lactamase in bacterial resistance?
Inactivation of penicillin by bacterial β-lactamase.
Which penicillin combination is not active against MRSA?
Amoxicillin + Clavulanic acid (Augmentin®)
What is the primary route of excretion for Penicillin G?
About 10% by glomerular filtration and 90% by tubular secretion.
How can probenecid affect penicillin levels?
Probenecid can partially block tubular secretion, providing higher systemic levels of penicillin.
What is a common adverse effect associated with penicillins?
Allergy (all forms).
