37 Questions
What is the primary function of β-lactamases?
Inactivate β-lactam antibiotics
How does the hydrolytic regeneration of the active site in β-lactamases compare to cell wall transamidase?
More efficient
Where are β-lactamases usually shed in gram-positive bacteria like staphylococci?
Outside the cell wall
What is a common expression of allergy to penicillin-type antibiotics?
Mild drug rash or itching
How does the allergenic reaction to penicillin-type antibiotics vary?
Delayed or immediate onset
What is the term used to classify an inhibitor that inhibits an enzyme irreversibly by undergoing subsequent reactions?
Mechanism-based inhibitor
Which compound enhances the potency against β-lactamase–producing strains when added to amoxicillin and ticarcillin preparations?
Clavulanic acid
How is sulbactam prepared?
By partial chemical synthesis from penicillins
Which functional group substitution in ticarcillin enhances its water solubility and potency against gram-negative organisms?
Carboxylic acid moiety
Which is a popular combination used clinically to combat β-lactamase-producing strains?
Clavulanic acid and ampicillin
What is the primary reason for the defective cell wall and inactivated enzyme due to β-lactam antibiotics?
Steric hindrance preventing regeneration of the active site
Why is water considered an insufficiently effective nucleophile in relation to cell wall transamidase inactivation by β-lactam antibiotics?
Steric barrier preventing hydrolysis of the complex
What contributes to the structural weakness of the resulting cell wall under the action of β-lactam antibiotics?
Covalent interruption due to enzyme inactivation
Why is resistance to β-lactam antibiotics alarming?
Mutated PBP-2 (PBP-2a) with decreased drug binding
In the context of β-lactam resistance, what is the more common mechanism than decreased cellular uptake or lower binding affinity to protein binding proteins?
Production of β-lactamases
What is the principal cause of bacterial resistance to beta-lactam antibiotics in the clinic?
β-lactamase catalyzed hydrolysis
What are the products formed when alcohols and amines react with beta-lactam antibiotics?
Esters and amides
How do proteins contribute to the formation of antigenic conjugates responsible for many penicillin allergies?
Through a specific primary amino group reaction
What term is used for small molecules that react with proteins to produce antigens?
Haptens
Why is the hydrolysis of the beta-lactam ring significant for the deactivation of beta-lactam antibiotics?
To prevent reclosure to penicillin
What modification to the cephalosporin structure leads to improved stability towards beta-lactamase?
Addition of a 7-alpha methoxyoxime
Which modification is essential for the antimicrobial activity of cephalosporins?
Addition of an amino group at the alpha position
What structural change is responsible for improved antibacterial activity in cephalosporins?
Replacement of the hydrogen at C-7 with an alkoxy group
Which structural feature contributes to blocking the inhibitor's affinity for the enzyme?
Incorporation of a lactone ring
Which modification results in improved stability of the beta-lactam in cephalosporins under acidic conditions?
Addition of an amino group at the alpha position
What is the molecular mode of action of beta-lactam antibiotics?
Inhibition of enzymes processing peptidoglycan layer
In the context of cell wall cross-linking, what role do penicillin-binding proteins (PBPs) play?
Facilitating cross-linking of the cell wall peptidoglycan
What is the major mechanism by which beta-lactam antibiotics exhibit bactericidal activity?
Inhibiting cell wall synthesis through enzyme inactivation
Which structural feature contributes to the resistance of nafcillin and dicloxacillin to enzyme degradation?
D-alanine-d-alanine unit termination
What is the primary consequence of β-lactam antibiotics reacting with penicillin-binding proteins (PBPs) according to Path B?
Inhibition of cell wall cross-linking
What is the enzyme responsible for metabolizing imipenem through hydrolysis of the β-lactam, deactivating it?
Renal dehydropeptidase-1
Which carbapenem has a chiral methyl group at C-4, conferring intrinsic resistance to hydrolysis by dehydropeptidase-1?
Meropenem
What is the inhibitor coadministered with imipenem to protect it from metabolic deactivation by renal dehydropeptidase-1?
Cilastatin
Which carbapenem is considered more potent against Pseudomonas species compared to imipenem and meropenem?
Doripenem
What synthetic monocyclic β-lactam antibiotic has an antimicrobial spectrum devoted almost exclusively to gram-negative microorganisms?
Aztreonam
Which carbapenem is not active against Pseudomonas or Acinetobacter?
Ertapenem
What group confers stability toward dehydropeptidase-1 for both doripenem and ertapenem?
4-β-methyl group
Test your knowledge on how steric hindrance can lead to enzymatic inactivation and defective cell wall formation in the context of β-lactam bond cleavage. Explore the impact of relief of strain on enzymatic reactions and the role of water as a nucleophile.
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