Questions and Answers
Which of the following are considered 'ESKAPE' pathogens? (Select all that apply)
What does VRE stand for?
Vancomycin-resistant Enterococcus
What type of resistance mechanism is mainly caused by ß-lactamase?
Inactivation of antibiotic
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?
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What is the primary use of amoxicillin?
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Match the following penicillins to their characteristics:
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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
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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.
