Questions and Answers
What are the 4 β-lactam antibiotic classes that selectively inhibit cell wall synthesis?
What determines the selective toxicity of β-lactam antibiotics?
Specific actions on the bacterial cell wall.
Antibiotics with what type of activity can interfere with β-lactam antibiotics?
Bacteriostatic.
Are β-lactam antibiotics bacteriostatic?
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β-lactam antibiotics are synergistic with which antibiotic class?
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What is the structure of penicillins?
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How do penicillins work?
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Why are penicillins relatively ineffective against G- microbes?
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What are the limitations of Penicillin G?
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What is Pfizerpen?
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What organisms can be treated with Penicillin G?
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Penicillin G is the DOC for which microbes?
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Penicillin G is indicated for staphylococcal infection unless a culture shows the organism lacks penicillinase.
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What is Penicillin VK indicated for?
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What are depot penicillins?
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What are the antistaphylococcal penicillins?
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Which antistaphylococcal penicillins are given via intermittent IV infusion?
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Dicloxacillin is indicated for what type of infections and how is it administered?
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Study Notes
β-Lactam Antibiotic Classes
- Four classes: Penicillins, Cephalosporins, Carbapenems, Monobactam.
- All contain a 4-membered β-lactam ring, crucial for their function.
Selective Toxicity
- Target bacterial cell wall synthesis, absent in mammalian cells.
- Effective only against actively growing bacteria by inhibiting cross-linkage of peptide chains.
Interference with Other Antibiotics
- Bacteriostatic antibiotics can hinder the action of β-lactam antibiotics, which are bactericidal and require active bacterial proliferation.
Killing Mechanism
- β-Lactam antibiotics exert time-dependent killing and are bactericidal.
Synergistic Effects
- Exhibit synergy with aminoglycosides, enhancing antibacterial efficacy.
Structure of Penicillins
- Composed of a 5-membered thiazolidine ring with a sulfa component.
Mechanism of Action for Penicillins
- Inhibit final step of cell wall synthesis (transpeptidation).
- Bind to penicillin-binding proteins (PBPs) in bacterial membranes, preventing essential cross-linkages in peptidoglycan.
Limitations Against Gram-Negative Bacteria
- Effectiveness reduced due to the outer lipopolysaccharide layer of Gram-negative bacteria which obstructs penicillins.
Limitations of Penicillin G
- Instability at acid pH necessitates IV or IM administration.
- Susceptible to β-lactamase.
- Limited activity against Gram-negative bacilli.
Clinical Uses of Penicillin G
- Treats various infections caused by Gram-positive cocci such as S.pyogenes, S.pneumoniae, and Enterococcus.
- Also effective against specific Gram-negative cocci, bacilli, and spirochetes like T.pallidum (syphilis).
Drug of Choice (DOC)
- Penicillin G is the DOC for meningococcal meningitis (N.meningitidis), gas gangrene (C.perfringens), and syphilis (T.pallidum).
Indication Limitations
- Not recommended for staphylococcal infections unless penicillinase is absent in the organism.
Penicillin VK Characteristics
- Poor bioavailability limits use to minor infections.
- Increased acid stability allows for oral administration.
Depot Penicillins
- Include Bicillin L-A (100% benzathine penicillin G) and mixtures like Bicillin C-R.
- Administered via IM injection for extended duration of action.
Antistaphylococcal Penicillins
- Include Nafcillin, Oxacillin, and Dicloxacillin.
- Narrow spectrum, resistant to staphylococcal β-lactamases, used primarily for infections caused by penicillinase-producing staph.
Administration of Antistaphylococcal Penicillins
- Nafcillin and oxacillin are given via intermittent IV infusion for serious systemic infections.
Dicloxacillin Use
- Acid-stable, administered orally for non-serious conditions; absorption affected by food.
Key Notes
- Focus on the specific bacterial types susceptible to each antibiotic class.
- Understand the implications of β-lactam resistance mechanisms in clinical settings.
- Remember the conditions under which each type of penicillin is most effective for treatment.
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Description
Explore the essential classes of β-lactam antibiotics that target bacterial cell wall synthesis. This quiz covers key information such as the four main classes and how selective toxicity is achieved. Perfect for students studying pharmacology or microbiology.
