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Questions and Answers
Which of the following are classified as ESKAPE pathogens? (Select all that apply)
What does VRE stand for?
Vancomycin-resistant Enterococcus
What is the primary mechanism of action of penicillins?
Interference with cross-linkage of peptidoglycan cell wall
Penicillins are effective against viruses.
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Which bacterial cell wall components do penicillins inhibit?
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Which penicillin is known to be toxic and is not clinically used anymore?
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The outer membrane in gram-negative bacteria blocks ___ soluble penicillins.
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Which penicillins are semisynthetic and have an antibacterial spectrum similar to penicillin G?
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Study Notes
ESKAPE Pathogens
- Group of pathogens that escape antibacterial effects, posing significant treatment challenges.
- Includes:
- Enterococcus faecium (vancomycin-resistant E.faecium - VRE)
- Staphylococcus aureus (methicillin-resistant S.aureus - MRSA)
- Klebsiella pneumoniae (carbapenem-resistant)
- Acinetobacter baumannii
- Pseudomonas aeruginosa (fluoroquinolone-resistant and multidrug-resistant)
- Enterobacter species
- MDR Escherichia coli
Bacterial Cell Walls
-
Gram-positive:
- Have thicker peptidoglycan layers.
- Easily traversed by penicillins.
-
Gram-negative:
- Possess an outer lipopolysaccharide membrane that blocks water-soluble penicillins.
- Contains porins allowing transmembrane entry of specific penicillins.
Mechanism of Action of Penicillins
- Interfere with the cross-linkage of peptidoglycan cell wall, leading to osmotic instability and potential cell lysis.
- Primarily effective against rapidly growing organisms that actively synthesize peptidoglycan.
- Ineffective against mycobacteria, protozoa, fungi, and viruses.
Penicillin Structure and Action
- Composed of N-acetylglucosamine and N-acetylmuramic acid subunits.
- Penicillin-binding proteins (PBPs) are crucial for forming cross-links in the bacterial cell wall.
- Beta-lactam ring of penicillin permanently blocks the PBP active site, inhibiting bacterial cell wall synthesis.
Types of Penicillins
-
Natural Penicillins:
- Includes Penicillin G (IV use) and Penicillin V (oral use).
- Susceptible to beta-lactamases; Penicillin V has poor bacteremia absorption.
-
Antistaphylococcal Penicillins:
- Methicillin, nafcillin, oxacillin, dicloxacillin; designed to resist beta-lactamases.
- Target penicillinase-producing Staphylococci but no efficacy against gram-negative bacteria.
- Methicillin is not clinically used due to toxicity (risk of interstitial nephritis).
-
Extended-Spectrum Penicillins:
- Ampicillin and amoxicillin with broader activity against gram-negative bacilli.
- Effective in treating respiratory infections and preventing bacterial endocarditis.
- Efficacy enhanced by beta-lactamase inhibitors like clavulanic acid and sulbactam.
-
Antipseudomonal Penicillins:
- Specific details not provided. Their development targets infections caused by Pseudomonas aeruginosa.
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Description
Explore essential concepts in Pharmacology II focusing on Cell Wall Inhibitors I. This quiz will delve into 'ESKAPE' pathogens, highlighting their resistance mechanisms against antibacterial treatments. Test your knowledge on critical bacteria such as MRSA and VRE.
