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Questions and Answers
Which of the following are considered 'ESKAPE' pathogens? (Select all that apply)
Which of the following are considered 'ESKAPE' pathogens? (Select all that apply)
What does VRE stand for?
What does VRE stand for?
Vancomycin-resistant Enterococcus
What type of resistance mechanism is mainly caused by ß-lactamase?
What type of resistance mechanism is mainly caused by ß-lactamase?
Inactivation of antibiotic
Penicillins interfere with cross-linkage of _____ cell wall.
Penicillins interfere with cross-linkage of _____ cell wall.
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Which of the following penicillins is known for being toxic due to interstitial nephritis?
Which of the following penicillins is known for being toxic due to interstitial nephritis?
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What is the primary use of amoxicillin?
What is the primary use of amoxicillin?
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Match the following penicillins to their characteristics:
Match the following penicillins to their characteristics:
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Gram-positive bacteria have a thicker peptidoglycan layer than gram-negative bacteria.
Gram-positive bacteria have a thicker peptidoglycan layer than gram-negative bacteria.
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Study Notes
ESKAPE Pathogens
- ESKAPE pathogens are known for their ability to evade antibacterial effects.
- Key pathogens include:
- Enterococcus faecium (vancomycin-resistant, VRE)
- Staphylococcus aureus (methicillin-resistant, MRSA)
- Klebsiella pneumoniae (carbapenem-resistant)
- Acinetobacter baumannii
- Pseudomonas aeruginosa (fluoroquinolone-resistant and multidrug-resistant)
- Enterobacter species
- Multidrug-resistant Escherichia coli
Bacterial Cell Wall Characteristics
- Gram-positive bacteria: have a thicker peptidoglycan layer, easily penetrable by penicillins.
- Gram-negative bacteria: possess an outer lipopolysaccharide membrane that blocks water-soluble penicillins but allows entry through porins.
- Key components in bacterial cell wall include N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM).
Mechanism of Action of Penicillins
- Penicillins disrupt the cross-linkage of the peptidoglycan cell wall, leading to cell lysis due to osmotic pressure or autolysin activation.
- Primarily effective against rapidly dividing bacteria; ineffective against mycobacteria, protozoa, fungi, and viruses.
- Penicillins inhibit penicillin-binding proteins (PBPs), crucial for bacterial cell wall stability.
Penicillin Structure and Function
- PBPs facilitate the cross-linking of cell wall strands; penicillin binds to PBP active sites, blocking function.
- The beta-lactam ring of penicillin forms a permanent covalent bond with PBPs, inhibiting bacterial growth.
Types of Penicillins
-
Natural Penicillins:
- Penicillin G and V, susceptible to beta-lactamases.
- Penicillin V has poor absorption and is not used for bacteremia.
-
Antistaphylococcal Penicillins (ß-lactamase-resistant):
- Include Methicillin, Nafcillin, Oxacillin, and Dicloxacillin, specifically targeting penicillinase-producing staphylococci.
- Methicillin is toxic and not used clinically anymore due to interstitial nephritis.
-
Extended-Spectrum Penicillins:
- Ampicillin and Amoxicillin, effective against both gram-positive and some gram-negative bacteria.
- Used for respiratory infections and to prevent bacterial endocarditis during dental procedures.
- Beta-lactamase inhibitors like clavulanic acid and sulbactam enhance effectiveness against resistant strains.
-
Antipseudomonal Penicillins:
- Piperacillin and Ticarcillin, effective against various gram-negative bacilli but ineffective against Klebsiella due to penicillinase production.
Resistance Mechanisms
- Major causes of resistance include:
- Inactivation of antibiotics by beta-lactamase enzymes.
- Modification of target PBPs, reducing drug binding.
- Impaired penetration of the antibiotic to target PBPs.
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Description
Test your knowledge on ESKAPE pathogens and the characteristics of bacterial cell walls. This quiz will cover the mechanisms of action of penicillins and key features of gram-positive and gram-negative bacteria. Ideal for microbiology students and healthcare professionals.
