Non-Beta Lactam Antibiotics Flashcards
(15 cards)
Which of the following antibiotics inhibits bacterial cell wall synthesis by binding to D-Ala-D-Ala terminus of peptidoglycan precursors?
A. Vancomycin
B. Polymyxin B
C. Daptomycin
D. Fosfomycin
A
Vancomycin – Binds D-Ala-D-Ala to prevent peptidoglycan cross-linking
What is the mechanism of action of daptomycin?
A. Inhibits 30S ribosomal subunit
B. Inhibits DNA gyrase
C. Inserts into cell membrane causing depolarization
D. Binds to penicillin-binding proteins
C
Inserts into cell membrane causing depolarization – Daptomycin causes rapid ion loss and cell death
Which antibiotic is associated with muscle toxicity and requires monitoring of CPK?
A. Vancomycin
B. Daptomycin
C. Polymyxin E (colistin)
D. Fosfomycin
B
Daptomycin – Monitor CPK; risk of rhabdomyolysis
Which drug is often used as a last-resort treatment for multidrug-resistant Gram-negative infections and disrupts the bacterial outer membrane?
A. Linezolid
B. Polymyxin B
C. Fosfomycin
D. Meropenem
B
Polymyxin B – Last-line for MDR Gram-negatives, disrupts membrane
Which of the following drugs inhibits the first step in bacterial cell wall synthesis by inactivating enolpyruvyl transferase (MurA enzyme)?
A. Daptomycin
B. Vancomycin
C. Fosfomycin
D. Colistin
C
Fosfomycin – Blocks MurA enzyme, early step of peptidoglycan synthesis
Which statement is TRUE about polymyxins?
A. They are effective against Gram-positive bacteria
B. They work by inhibiting protein synthesis
C. They are nephrotoxic and neurotoxic
D. They target DNA replication
C
They are nephrotoxic and neurotoxic – Especially colistin
Which non-beta-lactam agent is ineffective for pneumonia because it is inactivated by pulmonary surfactant?
A. Fosfomycin
B. Daptomycin
C. Colistin
D. Vancomycin
B
Daptomycin – Inactivated by lung surfactant
Which antibiotic works on the cell wall but is safe to use in patients with severe penicillin allergy?
A. Ceftriaxone
B. Meropenem
C. Vancomycin
D. Piperacillin-tazobactam
C
Vancomycin – Glycopeptide, safe in penicillin allergy
Explain the mechanism of action of vancomycin. How does it differ from beta-lactams?
Vancomycin binds to the D-Ala-D-Ala terminus of peptidoglycan precursors, preventing transglycosylation and transpeptidation. Unlike beta-lactams, which bind PBPs, vancomycin works outside the cell membrane and does not rely on PBPs.
Name two key side effects of polymyxins. Why are these drugs considered last-line?
Side effects: Nephrotoxicity, neurotoxicity. Used as last-line due to toxicity and emergence of resistance.
Describe why daptomycin cannot be used for pneumonia.
Daptomycin is inactivated by pulmonary surfactant, so it is ineffective in pneumonia. It is better used for bloodstream or soft tissue infections.
Compare the spectrum of activity between vancomycin and polymyxins.
Vancomycin: Gram-positive (MRSA, Enterococcus)
Polymyxins: Gram-negative (Pseudomonas, Acinetobacter, Klebsiella)
What is the mechanism of resistance to vancomycin seen in Enterococcus?
Resistance via altered target site: Enterococci replace D-Ala-D-Ala with D-Ala-D-Lac, reducing binding affinity.
Which drug is commonly used for uncomplicated UTI and inhibits cell wall synthesis at the early stage? Explain its mechanism briefly.
Fosfomycin – Used in UTI. Inhibits MurA enzyme, preventing the first step in cell wall synthesis.
Why is fosfomycin often given as a single-dose treatment for uncomplicated UTIs?
Fosfomycin achieves high urinary concentration, has a long half-life, and is well-tolerated, making it effective as a single dose in uncomplicated cystitis.
