Non-β-Lactam Antibiotics: Tetracyclines Overview
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Questions and Answers

Which enzyme is responsible for O-adenylation?

  • Adenyl synthetase (correct)
  • Streptidine synthetase
  • Phosphoryl transferase
  • Glucosamine transferase

The primary functional group in aminoglycosides is a hydroxyl group.

False (B)

What is the pharmacophoric unit mentioned in the content?

1,3-Diamino inositol

Adenyl synthetase makes __________.

<p>O-adenylation</p> Signup and view all the answers

Match the following compounds with their associated components:

<p>Streptidine = An aminoglycoside component 2-deoxy streptamine = Building block in aminoglycosides N-methyl glucosamine = Variation in glucosamine structure Aminocyclitol = Core structure in many antibiotics</p> Signup and view all the answers

What is one reason why tetracycline is not recommended for pregnant women?

<p>It causes discoloration of teeth in the fetus. (D)</p> Signup and view all the answers

Outdated tetracycline can cause super infections in the intestine.

<p>False (B)</p> Signup and view all the answers

What condition can arise from the overgrowth of Candida due to tetracycline use?

<p>Vaginal infections</p> Signup and view all the answers

Tetracycline causes __________ discoloration and hypoplasia of teeth in growing children.

<p>teeth</p> Signup and view all the answers

Match the following effects of tetracycline with their descriptions:

<p>Discoloration of teeth = Caused by chelation with Ca2+ Renal damage = A risk of using outdated tetracycline Super infections = Overgrowth of Candida or resistant bacteria Photosensitive reactions = Allergic reactions to sunlight exposure</p> Signup and view all the answers

What is the primary pharmacophore of the tetracycline group mentioned?

<p>Sancycline (C)</p> Signup and view all the answers

Tetracycline is not recommended for children younger than 8 years due to possible tooth damage.

<p>True (A)</p> Signup and view all the answers

What is a degradation product mentioned in the content?

<p>4-epianhydrotetracyclines (A)</p> Signup and view all the answers

The 4-epianhydrotetracyclines are known to be beneficial for kidney health.

<p>False (B)</p> Signup and view all the answers

At which pH range does epimerization occur?

<p>pH 2-6</p> Signup and view all the answers

The formation of _______ leads to an inactive configuration.

<p>4-Epimertetracycline</p> Signup and view all the answers

Match the compound with its characteristic:

<p>4-epianhydrotetracyclines = Toxic to kidneys 4-Epimertetracycline = Inactive configuration Epimerization = Occurs between pH 2-6 Tetracyclines = Degradation product</p> Signup and view all the answers

Which of the following statements about tetracyclines is true?

<p>They can undergo epimerization. (B)</p> Signup and view all the answers

4-epianhydrotetracyclines are formed when tetracyclines lose their effectiveness.

<p>True (A)</p> Signup and view all the answers

What configuration do 4-Epimertetracyclines have?

<p>Beta configuration</p> Signup and view all the answers

The chemical structure CH3 N(CH3)2 represents a compound with a _______ group.

<p>dimethylamine</p> Signup and view all the answers

Which of the following antibiotics is a tetracycline analogue?

<p>Tigecycline (C)</p> Signup and view all the answers

Tigecycline is active against Pseudomonas infections.

<p>False (B)</p> Signup and view all the answers

What mechanisms of resistance do tetracycline analogues overcome?

<p>Acquired efflux pumps and ribosomal protection</p> Signup and view all the answers

The prototype aminoglycoside antibiotic is __________.

<p>Streptomycin</p> Signup and view all the answers

Match the following aminoglycosides with their characteristics:

<p>Neomycin = Must not be given parenterally due to high toxicity Streptomycin = First used prototype of this class Aminoglycosides = Broad spectrum but limited use for severe G-ve infections</p> Signup and view all the answers

Which of the following is NOT a characteristic of aminoglycosides?

<p>Can be taken orally for systemic infections (D)</p> Signup and view all the answers

Aminoglycosides are effective against anaerobic bacteria.

<p>False (B)</p> Signup and view all the answers

What is one major side effect associated with aminoglycosides?

<p>Ototoxicity</p> Signup and view all the answers

Due to their high toxicity, neomycin is used __________ or __________.

<p>topically, orally</p> Signup and view all the answers

Match the source with the aminoglycosides:

<p>Streptomyces = Ends with suffix 'mycin' Micromonospora = Ends with suffix 'micin' Aminoglycosides = Obtained from microorganisms in soil</p> Signup and view all the answers

What is the primary reason aminoglycosides are not absorbed from the gastrointestinal tract?

<p>Their polar structure prevents absorption. (B)</p> Signup and view all the answers

Aminoglycosides can be mixed with β-lactam antibiotics in the same solution without any issue.

<p>False (B)</p> Signup and view all the answers

What type of bacteria do aminoglycosides target?

<p>Bacteria that synthesize proteins.</p> Signup and view all the answers

Aminoglycosides exert a synergistic action with β-lactam antibiotics when given into different tissue ________.

<p>compartments</p> Signup and view all the answers

Match the following mechanisms with their descriptions:

<p>Permeability defect = Outer membrane change prevents active transport into cell Lack of receptor = Lower binding affinity on the 30 S subunit R-factor enzymes = Enzymes that destroy drugs through acetylation</p> Signup and view all the answers

Which of the following describes the action of aminoglycosides?

<p>Inhibition of protein synthesis. (B)</p> Signup and view all the answers

Aminoglycosides can be excreted in urine in an inactive form after injection.

<p>False (B)</p> Signup and view all the answers

What type of structure allows aminoglycosides to exist as polycations at physiological pH?

<p>Strongly basic compounds</p> Signup and view all the answers

The enzyme ________ is involved in acetylation of aminoglycosides, leading to drug inactivation.

<p>Acetyl transferase</p> Signup and view all the answers

What is required for aminoglycosides to effectively bind to the ribosome?

<p>Presence of a specific receptor protein. (C)</p> Signup and view all the answers

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Flashcards

What are tetracyclines?

Tetracyclines are a class of antibiotics that work by inhibiting protein synthesis in bacteria. They are effective against a wide range of bacterial infections, including those of the respiratory tract, urinary tract, and skin.

Why should tetracyclines be avoided in children and pregnant women?

Tetracyclines can cause discoloration of teeth in children and pregnant women due to their affinity for calcium, which is essential for tooth development.

What other use do tetracyclines have?

Tetracyclines can be used to treat acne as they suppress the growth of Propionibacterium acnes, a bacteria that contributes to acne development.

What side effect can tetracyclines have on the skin?

Tetracyclines can cause photosensitivity reactions, making skin more susceptible to sunburn. It is important to wear sunscreen and avoid excessive sun exposure while taking tetracyclines.

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How do tetracyclines work at the molecular level?

Tetracyclines work by binding to the 30S ribosomal subunit, which is essential for protein synthesis in bacteria. This binding inhibits the translation of mRNA into proteins, ultimately leading to bacterial death.

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What is the concern with outdated tetracyclines?

Outdated tetracyclines can be toxic to the kidneys. It is important to obtain tetracyclines from trusted sources and follow proper storage guidelines.

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How can tetracyclines affect the body's microbiome?

Tetracyclines can disrupt the normal bacterial balance within the body, leading to overgrowth of Candida in the vagina or resistant Staphylococci in the intestine.

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Tetracyclines

A group of antibiotics known for their broad-spectrum action against bacteria. They work by inhibiting protein synthesis in bacteria, thus preventing their growth and multiplication.

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4-Epianhydrotetracyclines

A modification of the tetracycline molecule that occurs at carbon position 4, leading to the formation of an anhydride ring.

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Epimerization at C4

The process of converting a tetracycline molecule into its 4-Epianhydrotetracycline form.

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Epimerization

A change in the three-dimensional arrangement of atoms in a molecule, particularly at a specific carbon atom.

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Degradation

The process of breaking down a chemical compound, often resulting in the formation of new molecules.

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Chemical Stability

A particular property of a chemical compound that refers to its tendency to remain stable and resist decomposition.

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pH

The level of acidity or alkalinity of a solution, measured on a scale from 0 to 14.

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Inactive

A state where a chemical compound loses its ability to exert its intended effect, often due to changes in its structure or properties.

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Toxic to the kidneys

A type of toxicity that specifically affects the kidneys, causing damage to these organs.

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Phosphoryl Transferase

An enzyme that transfers a phosphate group from a donor molecule to a hydroxyl (-OH) group on a target molecule.

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Adenyl Synthetase

An enzyme that adds an adenyl group (adenosine monophosphate) to a molecule.

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Aminoglycosides

A class of antibiotics that inhibit bacterial protein synthesis by binding to the 30S ribosomal subunit.

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Pharmacophore

A structural feature that is essential for a molecule's biological activity.

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1,3-Diamino Inositol

A cyclic sugar alcohol that is a core structural component of many aminoglycosides.

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Tetracycline Analogues

A class of antibiotics that includes tigecycline and glycylcyclines, which are synthetic derivatives of minocycline. They work similarly to tetracycline antibiotics but overcome common resistance mechanisms.

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Tigecycline

A tetracycline analogue that overcomes common tetracycline resistance mechanisms like efflux pumps and ribosomal protection. It is effective against a wide range of bacteria but not Pseudomonas.

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Streptomycin

The first aminoglycoside antibiotic discovered and used. It is produced by Streptomyces griseus.

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Aminoglycoside Properties

Aminoglycosides are basic due to their amino group. This makes them water soluble but poorly absorbed from the gut. Therefore, they are typically administered via injection.

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Aminoglycoside Target Infections

Aminoglycosides are most effective for severe, Gram-negative infections because they have a broad spectrum of activity against aerobic bacteria.

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Aminoglycoside Toxicity

Due to their high toxicity, aminoglycosides can cause ototoxicity (hearing damage) and nephrotoxicity (kidney damage).

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Neomycin

Neomycin, an aminoglycoside, is highly toxic and should not be given intravenously. It is used topically for skin infections and orally for local infections in the gut.

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Oral Aminoglycosides

Oral administration of aminoglycosides is generally reserved for treating local infections in the gastrointestinal tract.

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Aminoglycosides in Hepatic Coma

Aminoglycosides can reduce the bacterial population in the intestine, which is sometimes used in the treatment of hepatic coma.

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What is the key characteristic of aminoglycosides?

Aminoglycosides are a class of antibiotics that are strongly basic and exist as polycations at physiological pH. They are highly soluble in water due to their polar structure.

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How are aminoglycosides administered?

Aminoglycosides are poorly absorbed from the gastrointestinal tract (GIT) because of their polar structure. For this reason, they are typically administered via injection.

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How do aminoglycosides work?

Aminoglycosides work by inhibiting protein synthesis in bacteria. Specifically, they bind to the 30S subunit of the bacterial ribosome, preventing the initiation of protein synthesis.

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What happens when aminoglycosides are combined with β-lactams?

Aminoglycosides exhibit a synergistic effect with β-lactams, meaning they work better together. However, they cannot be mixed in the same solution due to chemical incompatibility.

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How can bacteria become resistant to aminoglycosides?

Bacterial resistance to aminoglycosides can arise through various mechanisms, including changes in outer membrane permeability, lack of specific protein receptors on the 30S subunit, and production of enzymes that destroy the drug.

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What is one mechanism of bacterial resistance to aminoglycosides?

One mechanism of bacterial resistance involves changes in the outer membrane permeability, preventing the aminoglycoside from reaching the ribosome.

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What is another mechanism of bacterial resistance to aminoglycosides?

Another mechanism of bacterial resistance involves the lack of specific protein receptors on the 30S subunit, which reduces the affinity of the binding site to aminoglycosides.

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What is a third mechanism of bacterial resistance to aminoglycosides?

Some bacteria produce enzymes, such as acetyltransferases, that modify the aminoglycosides, rendering them inactive.

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What is the function of acetyltransferases in bacterial resistance?

Acetyltransferases are enzymes that modify the amino group (NH2) of aminoglycosides, making them less effective.

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How are aminoglycosides eliminated from the body?

Aminoglycosides are excreted in an active form in the urine, resulting in high concentrations in the urine.

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Study Notes

Non-β-Lactam Antibiotics

  • Tetracyclines are obtained from fermentation procedures from Streptomyces species, natural sources.
  • Tetracyclines are bacteriostatic, highly lipophilic, and effective against Gram-positive and Gram-negative bacteria, Rickettsiae, Mycoplasma, Chlamydia and Cholera.
  • Tetracyclines are used to treat acute intestinal amoebiasis, malaria infections, and bacillary dysentery.
  • Appropriate tetracyclines are used to treat acne, promote inflammatory changes, and treat eye infections, pneumonia, and urinary tract infections.
  • Tetracyclines bind to the 30S ribosomal subunit of bacteria, blocking access of aminoacyl-tRNA to the acceptor site, inhibiting protein synthesis.
  • The mechanism of action involves forming a chelate compound with magnesium ions present at the binding site, blocking aminoacyl-tRNA from bringing another amino acid, which results in inhibition of protein synthesis.
  • Tetracyclines are strong metal-binders and remove essential metal ions as chelated compounds.
  • Adverse effects include gastric discomfort, deposition in bones and teeth during calcification in growing children, super infections, outdated tetracyclines can produce renal damage and photosensitivity.

Aminoglycosides

  • Aminoglycosides are obtained from Streptomyces or Micromonospora.

  • Aminoglycosides are bactericidal against aerobic gram-negatives.

  • Aminoglycosides inhibit protein synthesis at the 30S ribosomal subunit.

  • Aminoglycosides have nephrotoxicity and ototoxicity.

  • Aminoglycosides include Tobramycin, Amikacin, Neomycin, Gentamicin, and Streptomycin.

  • Aminoglycosides have side effects such as neurotoxicity, allergic reactions, nephrotoxicity, and ototoxicity.

  • The properties of aminoglycosides are due to highly polar structure.

  • Aminoglycosides cannot be absorbed through the GIT due to their highly polar structure.

  • Aminoglycosides are excreted through the urine following injection.

  • Aminoglycosides are incompatible and must not be combined with other antibiotics in the same solution.

  • Aminoglycosides inhibit protein synthesis.

    • Binding to the 30S ribosomal subunit of bacteria.
    • Inhibiting initiation of protein synthesis.

  • Aminoglycosides show bacterial resistance:

    • Permeability defect by outer membrane change.
    • Lack of specific receptor on 30S subunit
      • Decreased affinity for binding sites of aminoglycosides. -Production of enzymes (R-factor enzymes) that destroy drugs.

  • Examples of enzymes are:

    • Acetyl transferase enzyme,
    • Phosphoryl transferase enzyme,
    • Adenyl synthetase enzyme.

  • Spectinomycin is the drug of choice for treating gonorrhea caused by penicillinase-producing N. gonorrhea.

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Description

Explore the properties, uses, and mechanisms of tetracyclines, a critical subclass of non-β-lactam antibiotics. This quiz covers their bacteriostatic action, effectiveness against various bacteria, and clinical applications in treating infections. Test your knowledge on this important antibiotic class and its role in healthcare.

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