Antibiotics Classifications and Functions

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Questions and Answers

Which type of antibiotics primarily targets gram-negative organisms and is effective against Pseudomonas?

  • Macrolides
  • β-lactams
  • Aminoglycosides (correct)
  • Tetracyclines

What is the primary mechanism of action of macrolides like erythromycin, clarithromycin, and azithromycin?

  • Inhibit protein synthesis (correct)
  • Inhibit folate synthesis
  • Disrupt nucleic acid synthesis
  • Inhibit cell wall synthesis

Which antibiotic class has a synergistic action when combined with β-lactams?

  • Macrolides
  • Aminoglycosides (correct)
  • Lincosamides
  • Glycopeptides

Which of the following macrolides is NOT typically used in clinical practice?

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

Which statement about macrolides is false?

<p>They are effective only against gram-positive bacteria. (C)</p> Signup and view all the answers

Which antibiotic is considered the first choice for patients who are allergic to penicillins?

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

What advantage does clarithromycin have over erythromycin in treating certain infections?

<p>Higher activity against H. pylori (A)</p> Signup and view all the answers

Which of the following is NOT typically a first-line treatment for individuals allergic to penicillins?

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

In which scenario would erythromycin primarily be used?

<p>For patients with a known penicillin allergy (C)</p> Signup and view all the answers

Which feature is a distinguishing factor of clarithromycin compared to erythromycin?

<p>It has a stronger effect against H. pylori. (C)</p> Signup and view all the answers

What is a key characteristic of broad-spectrum antibiotics?

<p>They are effective against a wide variety of microbial species. (C)</p> Signup and view all the answers

Which statement accurately describes extended-spectrum antibiotics?

<p>They cover a broad range of gram-positive and significant gram-negative bacteria. (C)</p> Signup and view all the answers

Which of the following penicillins is classified as an antistaphylococcal penicillin?

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

Which of the following options best describes the spectrum of Benzyle Penicillins?

<p>Narrow spectrum primarily targeting Gram-positive bacteria (D)</p> Signup and view all the answers

Which of the following best differentiates extended-spectrum antibiotics from broad-spectrum antibiotics?

<p>Extended-spectrum antibiotics are modified for a broader action, to include more gram-positive and several gram-negative bacteria. (D)</p> Signup and view all the answers

Which of the following penicillins is NOT considered an extended-spectrum penicillin?

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

The term 'broad-spectrum' implies an antibiotic's effectiveness against which of the following?

<p>A wide variety of microbial species. (D)</p> Signup and view all the answers

Which of the following statements is false regarding the types of antibiotics?

<p>Extended-spectrum antibiotics are specifically modified for gram-positive bacteria. (A)</p> Signup and view all the answers

What characteristic defines antistaphylococcal penicillins like Methicillin and Cloxacillin?

<p>They are resistant to penicillinase-producing bacteria (D)</p> Signup and view all the answers

Which of the following best describes the relationship between extended-spectrum penicillins and narrow-spectrum penicillins?

<p>Extended-spectrum penicillins have a broader range of activity than narrow-spectrum penicillins (D)</p> Signup and view all the answers

Flashcards

Broad-spectrum antibiotics

Effective against a wide variety of bacterial species.

Extended-spectrum antibiotics

Modified to be effective against both gram-positive and gram-negative bacteria.

Gram-positive antibiotics

These antibiotics target gram-positive bacteria.

Gram-negative antibiotics

These antibiotics target gram-negative bacteria.

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Erythromycin

An antibiotic often used as an alternative to penicillins for individuals with penicillin allergies.

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Clarithromycin

An antibiotic with greater effectiveness against the bacteria H. pylori, a common cause of stomach ulcers.

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Narrow-Spectrum Penicillins

Penicillins that primarily work against gram-positive bacteria, particularly staphylococci. They are effective against a limited range of bacteria.

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Antistaphylococal Penicillins

A type of narrow-spectrum penicillin that is resistant to breakdown by bacterial enzymes, making it effective against penicillinase-producing staphylococci.

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Methicillin and Cloxacillin

Examples of antistaphylococal penicillins that are effective against many types of staphylococci.

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Extended-Spectrum Penicillins

Penicillins that have a wider range of activity against bacteria.

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Anaerobic antibiotics

These antibiotics primarily target gram-negative bacteria and Pseudomonas, needing oxygen for survival.

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Synergistic antibiotics

These antibiotics act in combination with beta-lactam antibiotics to enhance their effectiveness.

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Macrolides

A group of antibiotics that include erythromycin, clarithromycin, and azithromycin.

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Macrolide antibiotics

Erythromycin, clarithromycin, and azithromycin all belong to this class of antibiotics.

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Antibiotics that inhibit protein synthesis

These antibiotics work by interfering with protein synthesis in bacteria.

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Study Notes

Antibacterial Classification

  • Three main classes of antibiotics based on their mechanisms of action:
    • Inhibiting cell wall synthesis
    • Inhibiting protein synthesis
    • Inhibiting nucleic acid synthesis

Bacteriostatic vs Bactericidal

  • Bacteriostatic antibiotics prevent bacterial growth
  • Bactericidal antibiotics kill bacteria

Antibiotic Spectrum

  • Narrow-spectrum antibiotics target a specific group of microorganisms
  • Extended-spectrum antibiotics are effective against a wider range of gram-positive and gram-negative bacteria
  • Broad-spectrum antibiotics affect a large variety of microbial species

Beta-Lactams (Penicillins)

  • Mechanism of Action: Cell wall inhibitors
    • Bactericidal
  • Natural Penicillins: Narrow spectrum
  • Extended-Spectrum Penicillins: Wider spectrum
  • Clinical Uses:
    • Streptococcal infections
    • Salmonella infections
    • Spirochetes infections (syphilis, gonorrhea)
    • Staphylococcal infections
    • Rheumatic Fever
    • Prophylaxis in congenital heart disease
  • Adverse Effects:
    • Type I hypersensitivity reaction
    • Diarrhoea
  • Beta-Lactamase Inhibitors:
    • Combined with penicillins to protect them from enzymatic breakdown
    • Extend the antimicrobial spectrum

Cephalosporins

  • Clinical Uses:
    • Meningitis (3rd and 4th generation)
  • Adverse Effects:
    • Similar to penicillins
  • Cross-Sensitivity:
    • Some patients allergic to penicillins may also be allergic to cephalosporins (5-10% cross-reactivity)

Inhibitors of Protein Synthesis

  • Tetracyclines: bacteriostatic, broad-spectrum, used for various infections
    • Adverse effects: teeth discoloration, hepatotoxicity, phototoxicity
  • Aminoglycosides: (gentamicin, tobramycin) bactericidal; mainly effective against gram-negative bacteria, oxygen dependent, ineffective against anaerobes
    • Adverse effects: damage to the kidneys
  • Macrolides: (erythromycin, clarithromycin, azithromycin) bacteriostatic; wider spectrum; erythromycin preferred for penicillin allergy; clarithromycin and azithromycin used for H. pylori and Legionellosis, respectively.
    • Adverse effects: nausea, vomiting, abdominal pain
  • Chloramphenicol: broad-spectrum; bacteriostatic -Adverse effects: blood disorders and gray baby syndrome in newborns

Inhibitors of Nucleic Acid Synthesis

  • Quinolones: inhibit DNA gyrase; broad spectrum; used in UTI, respiratory infections, traveler's diarrhea
    • Adverse effects: tendon rupture, CNS symptoms, phototoxicity.
  • Sulfonamides and Trimethoprim: inhibit folate synthesis, bacteriostatic; used in UTIs, infections, and other infections
    • Adverse Effects: crystalluria, nephropathy, hypersensitivity reactions, bone marrow depression
  • Co-trimoxazole: combination of sulfamethoxazole and trimethoprim
    • More potent
    • Synergistic combination, wider spectrum
    • Used in tuberculosis

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