Antibiotics Quiz: Kanamycin and Tetracyclines
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Questions and Answers

Which of the following statements about Kanamycin is true?

  • Kanamycin does not have any glycosidic linkages.
  • Kanamycin undergoes phosphorylation at the -3'-OH group. (correct)
  • Kanamycin is a type of aminoglycoside antibiotic. (correct)
  • Kanamycin A, B, and C are all unstable to R-factor enzymes.

Dihydrostreptomycin has a higher likelihood of causing delayed deafness than streptomycin.

True (A)

What is the pharmacophoric group replacement in dihydrostreptomycin?

The aldehydic group is replaced by an alcoholic group (CH2OH).

Kanamycin consists of a mixture of Kanamycin A, B, and __.

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

Match the following effects with their corresponding groups involved in inactivation by R-factor enzymes:

<p>-3'-OH = Phosphorylation 4'-OH = Adenylation 6'-NH2 = Acetylation -OH = No effect</p> Signup and view all the answers

What is the primary action of tetracyclines?

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

Tetracyclines are used in high doses for short periods to treat infections.

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

What is the role of magnesium ions in the mechanism of action of tetracyclines?

<p>Magnesium ions are required for the binding of tetracyclines to the ribosomal binding site.</p> Signup and view all the answers

Tetracyclines block the access of _____ to the m-RNA complex.

<p>amino acyl t-RNA</p> Signup and view all the answers

Match the antibiotic use with the correct condition it treats:

<p>Ophthalmic tetracyclines = Eye infections Tetracyclines for pneumonia = Pneumonia treatment Tetracyclines for gonorrhea = Gonorrhea treatment Tetracyclines for urinary tract infections = Urinary tract infection treatment</p> Signup and view all the answers

Which of the following is an adverse effect associated with tetracyclines?

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

How do tetracyclines demonstrate their bacteriostatic action?

<p>By binding to the 30S ribosomal subunit and blocking amino acyl t-RNA access.</p> Signup and view all the answers

Which of the following is a class of tetracyclines?

<p>Semi-Synthetic Tetracyclines (B)</p> Signup and view all the answers

Doxycycline is primarily used to treat urinary tract infections.

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

What is the primary route of excretion for the metabolite mentioned?

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

Doxycycline can be used for prophylaxis against __________.

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

What toxicity is associated with using minocycline?

<p>Vestibular toxicities (D)</p> Signup and view all the answers

Match the following tetracyclines with their characteristics:

<p>Doxycycline = Used in prophylaxis against malaria Minocycline = Known for vestibular toxicities Semi-Synthetic Tetracyclines = More lipophilic for better blood levels Natural Tetracyclines = Less effective in current clinical use</p> Signup and view all the answers

Once daily administration is a characteristic of semi-synthetic tetracyclines.

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

The chemical name for minocycline starts with 4-Dimethylamino-1,4,4a,5,5a,6,11,12a-octahydr- __________.

<p>3,6,10,12,12a-pentahydroxy-6-methyl-1,11-dioxo-2-naphthacene carboxamide</p> Signup and view all the answers

What advantage do semi-synthetic tetracyclines offer for oral administration?

<p>better blood levels</p> Signup and view all the answers

Which tetracycline is known to enter the cerebrospinal fluid (CSF) in sufficient levels for therapeutic efficacy?

<p>Minocycline (D)</p> Signup and view all the answers

All tetracyclines are stable against acids and bases.

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

What is the term used to describe the chemical modification of a compound through synthetic processes?

<p>Semi-synthesis</p> Signup and view all the answers

The class of antibiotics that includes Minocycline is called __________.

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

What type of enzyme is responsible for the phosphorylation of the OH group?

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

Adenyl synthetase is responsible for O-adenylation.

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

Match the following tetracyclines to their specific characteristics:

<p>Minocycline = Therapeutic efficacy in CSF Demeclocycline = Semi-synthesis involved Sancycline = Similar structure to tetracyclines Tetracycline = Broad-spectrum antibiotic</p> Signup and view all the answers

Which of the following processes is used in the synthesis of Minocycline?

<p>Reductive methylation (B), Catalytic reduction (C)</p> Signup and view all the answers

What is the primary pharmacophoric unit mentioned in the content?

<p>1,3-diamino inositol</p> Signup and view all the answers

Tetracyclines are only effective against bacterial infections.

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

The aminoglycoside structures include the unit of _____ for their functionality.

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

What are the five double bonds in the structure of Octahydronaphthacene used for?

<p>Stability and reactivity</p> Signup and view all the answers

Match the following aminoglycosides with their components:

<p>Streptidine = O-adenylation 2-deoxy streptamine = NH2 group base L-Streptose = Sugar component Glucosamine = Amino sugar</p> Signup and view all the answers

Tetracyclines are known for their broad spectrum of activity, especially against __________ infections.

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

Which group is present in aminoglycosides that contributes to their activity?

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

Phosphoryl transferase enzymes and adenyl synthetase serve the same function.

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

Match the following chemical processes with their descriptions:

<p>Nitration = Process of introducing a nitro group Reductive methylation = Adding methyl groups through reduction Catalytic reduction = Altering compounds using a catalyst Semi-synthesis = Modification of a natural product</p> Signup and view all the answers

What structural component is indicated by NH2 in aminoglycosides?

<p>Amino group</p> Signup and view all the answers

In the context of aminoglycosides, the OH group facilitates _____ transfer.

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

Which molecule is not an aminoglycoside mentioned?

<p>Chloramphenicol (D)</p> Signup and view all the answers

Flashcards

Tetracycline Mechanism of Action

Tetracyclines are a class of antibiotics that act by inhibiting protein synthesis in bacteria.

Bacteriostatic

Tetracyclines are bacteriostatic, meaning they stop bacterial growth rather than killing the bacteria directly.

Tetracycline Binding Site

Tetracyclines bind to the 30S ribosomal subunit of bacteria, blocking the access of aminoacyl tRNA to the mRNA complex. This prevents protein synthesis, as amino acids are essential for building proteins.

Chelate Compound Formation

Tetracyclines form a chelate compound with magnesium ions present at the binding site on the 30S ribosomal subunit. This complex prevents the binding of aminoacyl tRNA, stopping protein synthesis.

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Magnesium Ion Importance

Both the binding of aminoacyl tRNA and tetracyclines to the ribosomal binding site require magnesium ions. Tetracyclines' strong binding properties with metal ions suggest that their antibacterial activity may be due to their ability to remove essential metal ions like magnesium as chelated compounds.

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Tetracycline Side Effects

Tetracyclines can cause gastric discomfort due to irritation of the gastric mucosa. Therefore, they are often taken with food.

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Tetracycline Applications

Tetracyclines have a wide range of uses including treating acne, eye infections, pneumonia, gonorrhea, and urinary tract infections.

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Tetracyclines

A class of antibiotics known for their broad-spectrum activity against bacteria.

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Broad-spectrum activity

A key feature of tetracyclines, they are effective against a wide variety of bacteria.

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Minocycline

A type of tetracycline with increased lipophilicity, leading to better oral absorption and longer duration of action.

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Lipophilicity

The ability of a substance to dissolve in fats or oils.

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Once-daily administration

A key advantage of minocycline, it can be administered once daily due to its prolonged action.

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Minocycline's enhanced properties

Minocycline's higher lipophilicity contributes to improved oral absorption and longer duration of action.

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Vestibular toxicities

A potential side effect of minocycline, causing dizziness, loss of balance, and nausea.

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Excellent blood levels

A key benefit of minocycline, it provides excellent blood levels after oral administration.

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Excretion

The process of removing waste products from the body.

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What do PPT enzymes do?

PPT enzymes transfer a phosphate group from ATP to a hydroxyl (OH) group on a molecule.

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What do adenyl synthetase enzymes do?

Adenyl synthetase enzymes attach an adenine molecule to a hydroxyl (OH) group.

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What is streptidine?

Streptidine is a cyclic sugar molecule with several amine groups. It is part of aminoglycoside antibiotics.

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What is 2-deoxystreptamine?

2-deoxystreptamine is a modified sugar molecule that is also part of aminoglycoside antibiotics.

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What is the pharmacophoric unit of aminoglycoside antibiotics?

The pharmacophoric unit of an aminoglycoside antibiotic is the 1,3-diamino inositol moiety. This part is crucial for its antibiotic activity.

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What is the free moiety of aminoglycosides?

Aminoglycosides have a free moiety which is the aminocyclitol unit.

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What is the aminocyclitol unit?

The aminocyclitol unit is a cyclic molecule with amine groups, similar to streptidine.

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6-OH group in Tetracyclines

The 6-OH group is a hydroxyl group attached to the 6th carbon atom of the tetracycline molecule. Its absence in minocycline is the reason for its resistance to acid degradation.

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Chemical Structure of Minocycline

The chemical structure of minocycline is similar to other tetracyclines but it lacks the 6-OH group and has a dimethylamine group at position 9.

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Demeclocycline

Demeclocycline is another semisynthetic tetracycline that is used primarily for the treatment of urinary tract infections.

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Sancycline

Sancycline is a tetracycline that is used to treat acne vulgaris.

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Therapeutic Spectrum of Tetracyclines

Tetracyclines are effective against a broad range of bacteria but are not effective against all bacteria.

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Tetracycline penetration into CSF

While tetracyclines can enter the CSF, their levels are typically insufficient for therapeutic efficacy, except for minocycline.

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Minocycline's use in meningitis

Minocycline's increased penetration into the CSF, the area surrounding the brain and spinal cord, makes it effective in treating meningitis.

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Common Uses of Tetracyclines

Tetracyclines are a class of antibiotics that are known for their broad spectrum of activity and their use in treating various infections.

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What is Dihydrostreptomycin?

Dihydrostreptomycin is formed by replacing the aldehydic group in the L-streptose moiety with an alcoholic group (CH2OH). This modification increases the likelihood of causing delayed deafness compared to streptomycin.

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What is the common core structure of Aminoglycosides?

Aminoglycosides are a class of antibiotics that share a common core structure, the 2-deoxystreptamine ring. This structure allows for modifications that impact antibiotic activity and toxicity.

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What are the variations of Kanamycin?

Kanamycin is an aminoglycoside antibiotic with three main forms: Kanamycin A, B and C. These variations differ in their chemical structures, specifically at the R1 and R2 positions, which affect their activity and stability.

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What is the significance of glycosidic linkages in Kanamycin?

The glycosidic linkage, which connects the different sugar moieties in Kanamycin (e.g., 3'-glucosamine, kanosamine), plays a crucial role in the antibiotic's activity. These linkages are targeted by resistance mechanisms in bacteria.

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How does Kanamycin become inactive?

Kanamycin is susceptible to bacterial resistance mechanisms, including phosphorylation, adenylation, and acetylation. These modifications affect specific functional groups on the molecule, rendering it inactive.

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Study Notes

Medicinal Chemistry I - Non β-Lactam Antibiotics

  • Tetracyclines are obtained through fermentation procedures from species of Streptomyces.
  • Tetracyclines are bacteriostatic and highly lipophilic, effective against both Gram-positive and Gram-negative bacteria, rickettsiae, mycoplasma, and chlamydia.
  • Tetracyclines are used to treat acute intestinal amoebiasis, malaria, and bacillary dysentery.
  • Tetracyclines can be used to treat acne by suppressing bacteria and their lipases.
  • Tetracyclines may be used in low doses for months.
  • Tetracyclines are used to treat various eye infections, pneumonia, gonorrhea, and urinary tract infections.

Mechanism of Action of Tetracyclines

  • Tetracyclines bind to the 30S ribosomal subunit of bacteria, preventing aminoacyl-tRNA from accessing the acceptor site.
  • This inhibits protein synthesis.
  • Tetracyclines can bind with magnesium ions at the ribosomal binding sites, blocking aminoacyl-tRNA.

Adverse Effects of Tetracyclines

  • Tetracyclines can cause gastric discomfort, so it's important to take them with food.
  • Tetracyclines can cause discoloration and hypoplasia of teeth in children, especially those under 8 years old. These effects are due to tetracyclines binding to calcium, thereby preventing normal bone and teeth development.
  • Tetracyclines can lead to superinfections, such as Candida overgrowth in the vagina or resistant Staphylococcus infections in the intestine.
  • Old, outdated tetracyclines can cause kidney damage.
  • Tetracyclines can cause photosensitive allergic reactions.

Chemical Stability of Tetracyclines

  • Strong acids dehydrate tetracyclines at C6, leading to the inactive form of anhydrotetracycline.
  • Tetracyclines without the 6-OH group are more resistant to acidic and basic conditions; also, they have higher lipid solubility, which enables better absorption.
  • Basic media transform tetracyclines with a 6-OH group into the inactive lactone form, Isotetracycline.
  • Epimerization at C4 leads to the inactive 4-epimertetracycline.

Classes of Tetracyclines

  • Tetracyclines are classified as natural and semi-synthetic.
  • Natural tetracyclines include tetracycline, chlortetracycline, and oxytetracycline.
  • Semi-synthetic tetracyclines include doxycycline and minocycline, which are primarily synthesized to target more specific areas of the body, such as the urinary tract versus a broader attack on bacteria in all areas of the body.

Aminoglycosides

  • Aminoglycosides are obtained from microorganisms, such as Streptomyces and Micromonospora.
  • Aminoglycosides are bacteriocidal agents, effective against aerobic Gram-negative bacteria mainly.
  • Aminoglycosides inhibit protein synthesis.
  • Aminoglycosides can cause neurotoxicity, allergic reactions, nephrotoxicity, and ototoxicity.
  • They have a highly basic structure hence in physiological pH conditions they act as polycations and are highly soluble in water.
  • Aminoglycoside antibiotics are not absorbed through the gastrointestinal tract due to their highly polar structure and are excreted in their active form in high concentration through the urine following injection.

Mechanism of Action of Aminoglycosides

  • Aminoglycosides bind irreversibly to the 30S ribosomal subunit of microbes.
  • This inhibits prokaryotic protein synthesis by interfering with the ability for the ribosomes to translate the mRNA.

Bacterial Resistance to Aminoglycosides

  • Aminoglycosides may experience permeability defects through the outer membrane of their target bacteria, preventing them from reaching the ribosome.
  • R-factor enzymes (e.g., acetyltransferases, phosphoryltransferases, and adenyltransferases) can modify aminoglycoside antibiotics.
  • Modified aminoglycosides lose their effectiveness and can also lead to adverse reactions.

Aminoglycosides with Structural Modification

  • Modifications of aminoglycosides, such as replacing the aldehydic group with an alcohol group, can improve their effect on the body.
  • 2-deoxy streptamine modifications can alter the properties of the antibiotic, thereby improving it or inhibiting it for particular uses.

Aminoglycosides with Different Structural Moieties

  • 1, 3-diaminoinositol moieties of aminocyclitol unit
  • Modifications in the structure may improve or inhibit the usefulness of the antibiotic for specific use cases.

Classes and Semi-synthetic Aminoglycosides

  • Aminoglycosides are classified based on structure.
  • Modifications can improve effectiveness by reducing resistance or broadening the spectrum.
  • Some examples include kanamycin, amikacin, tobramycin, and gentamicin.

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Test your knowledge on the properties and mechanisms of Kanamycin and Tetracyclines. This quiz covers various aspects including pharmacological effects, adverse reactions, and specific uses of these antibiotics. See how well you understand these important medications and their functions in treating infections.

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