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Questions and Answers
Who discovered penicillin in 1929?
Who discovered penicillin in 1929?
What is the historical significance of molded curd of soybean in Chinese folk medicine in relation to antibacterial antibiotics?
What is the historical significance of molded curd of soybean in Chinese folk medicine in relation to antibacterial antibiotics?
Used to treat boils and carbuncles
Antibiotics can either be bacteri_____(inhibit growth) or bacteri_____(kill) microorganisms.
Antibiotics can either be bacteri_____(inhibit growth) or bacteri_____(kill) microorganisms.
static, cidal
Match the type of antibiotics with their chemical classification:
Match the type of antibiotics with their chemical classification:
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What defines an antibiotic substance according to Waksman?
What defines an antibiotic substance according to Waksman?
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What structure is common to all eta-lactam antibiotics?
What structure is common to all eta-lactam antibiotics?
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What is the primary function of the bacterial cell wall?
What is the primary function of the bacterial cell wall?
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Penicillin inhibits the synthesis of __________, which provides strength and rigidity to the cell wall.
Penicillin inhibits the synthesis of __________, which provides strength and rigidity to the cell wall.
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Penicillin-Binding Proteins (PBPs) are involved in maintaining the round shape of bacteria.
Penicillin-Binding Proteins (PBPs) are involved in maintaining the round shape of bacteria.
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Match the following antibiotics with their target Penicillin-Binding Proteins (PBPs):
Match the following antibiotics with their target Penicillin-Binding Proteins (PBPs):
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What is the primary core nucleus responsible for the pharmacophore effect in penicillins?
What is the primary core nucleus responsible for the pharmacophore effect in penicillins?
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Study Notes
Antibacterial Antibiotics
Historical Overview
- Molded curd of soybean used to treat boils and carbuncles in Chinese folk medicine
- 1877: Pasteur and Joubert discovered that anthrax bacilli were killed by certain bacteria
- 1909: Ehrlich's discovery of Arsphenamine
- 1929: Fleming's discovery of penicillin
- 1935: Domagk's discovery of sulfa drugs
- 1938: Florey and Chain introduced penicillin in therapy
- Waksman defined antibiotics as substances produced by microorganisms that inhibit growth or destroy other microorganisms
Ideal Antibiotic
- Selectively toxic (magic bullet)
- Chemically stable
- Slow rate of elimination for dosing schedule, but rapid and complete removal
Commercial Production
- Preparation of pure culture
- Fermentation
- Isolation
- Purification
- Assays
- Formulation
Review of Bacteria
Differences between Bacterial and Animal Cells
- Bacterial cells lack a defined nucleus
- Bacterial cells are simpler and lack organelles
- Bacterial cells have a cell membrane and cell wall
- Biochemistry of bacterial cells differs from animal cells
- Ribosomes: 70S in bacteria, 60S + 40S in animals
Mechanisms of Antibacterial Action
- MOA of antibiotics varies
- Understanding MOA is basis for future development of antibacterial antibiotics
- Antibiotics can be either bacteriostatic (inhibit growth) or bactericidal (kill)
- Five mechanisms of antibacterial action:
- Inhibition of cell wall synthesis
- Interactions with DNA or RNA
- Inhibition of nucleic acid synthesis
- Disruption of protein synthesis
- Inhibition of cell metabolism
Specific Antibacterial Agents
- Chemical classification:
- Penicillins, cephalosporins (B-lactam ring)
- Tetracyclines (4-annulated rings)
- Aminoglycosides (amino sugars)
- Macrolides (large lactone ring)
- Bacitracins, polymyxins (polypeptides)
- Newer agents
Inhibitors of Cell Wall Synthesis
- B-lactam antibiotics
- Penicillins, cephalosporins, monobactams, and carbapenems
- Beta-lactam ring is responsible for antibacterial activity
The Bacterial Cell Wall
- Absent from mammalian cells
- Potential for selective chemotherapy
- Functions:
- Semipermeable barrier
- Barrier from osmotic pressure changes
- Prevent digestion by host enzymes
Beta-Lactam Antibiotics
- Possess B-lactam ring
- Penicillin G and Penicillin V are agents of choice
- Potent, rapid bactericidal action
- Low toxicity
- Inhibit synthesis of peptidoglycan
Penicillin-Binding Proteins (PBPs)
- PBP 1a, 1b, 2, 3, 4, 5, and 6
- Inhibition of PBPs leads to cell lysis or filamentous forms
- Different PBPs have different functions
The Penicillins
- Commercial production from Penicillium Chrysogenum
- Core nucleus: 6-aminopenicillanic acid (6-APA)
- Fermentation-derived: Pen G, Pen V, and 6-APA
- Sodium and potassium salts are crystalline, hydroscopic, and water soluble
Structure of Penicillin
- Beta-lactam ring
- Amino group
- Side chain (R-group)
- 6-APA is the core nucleus of penicillins
Nomenclature
- CAS: 6-acylamino-2,2-dimethyl-3-carboxylic acid
- USP: 4-thia-1-azabicycloheptone
- Simplified forms: "penam", "penicillanic acid", and "penicillin" + R-chain
Stereochemistry
- Three chiral centers: C2, C5, and C6
Biosynthesis of Penicillins
- Derived from two amino acids: L-cysteine and L-valine
- 6-APA is the core nucleus
Chemical Instabilities
- Most penicillins are acids
- Sodium and potassium salts are highly water-soluble
- Benzathine and procaine are poorly water-soluble (depot forms)
- Hygroscopic
Chemical Degradation
- Hydrolysis is the main cause of deterioration
- B-lactam amide bond is the most unstable bond
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Description
This quiz covers the introduction and historical overview of antibacterial antibiotics, including their mechanisms of action and specific types. It also touches on the concept of antibiosis and its discovery.
