antimicrobial II

PROTEIN SYNTHESIS INHIBITORS

• Dental Practice

  • Key antibacterial groups include:

    • A. Aminoglycosides

    • B. Macrolides

    • C. Tetracyclines

    • D. Lincosamides

    • E. Chloramphenicol

    • F. Linezolid

ANTIBIOTICS EFFECTIVE ON RIBOSOMAL SUBUNITS

• Bacterial 30S ribosomal subunit:

  • Aminoglycosides

  • Tetracyclines

• Bacterial 50S ribosomal subunit:

  • Chloramphenicol

  • Macrolides

CHLORAMPHENICOL

• Properties:

  • Bacteriostatic in nature

  • Broad-spectrum antibiotic

  • Bactericidal at higher concentrations against some organisms

• Mechanism of Action:

  • Binds reversibly to the 50S ribosomal subunit

  • Inhibits bacterial protein synthesis

• Clinical Uses:

  • Typhoid fever (alternative: Ciprofloxacin)

  • Topical antimicrobial agent

ADVERSE REACTIONS TO CHLORAMPHENICOL

• Common Issues:

  • Gastrointestinal disturbances

  • Risk of super-infection

  • Rare: Aplastic anemia, Gray baby syndrome (cyanosis)

TETRACYCLINES

• Types:

  • Tetracycline

  • Doxycycline

  • Demeclocycline

  • Minocycline

  • Oxytetracycline

• Mechanism of Action:

  • Binds to the 30S ribosomal subunit

  • Inhibits bacterial protein synthesis

• Therapeutic Uses:

  • Concentrated in gingival fluid; effective against resistant bacteria in chronic periodontal disease

  • Limited effectiveness in acute orodental infections, second choice to penicillin, erythromycin, cephalosporin, and clindamycin

• Additional Uses:

  • Eradication of H. Pylori

  • Malaria prevention

  • Treatment of amebiasis and acne

• Adverse Effects:

  • Heartburn, nausea, vomiting (no milk or antacid)

  • Alteration of normal flora (oral candidiasis, C. difficile colitis)

  • Bone and teeth issues: enamel hypoplasia, irregular bone growth (contraindicated in pregnancy and children)

MACROLIDES

• Types:

  • Erythromycin

  • Clarithromycin

  • Azithromycin

• Properties:

  • Narrow-spectrum bacteriostatic antibiotics

  • Effective against Gram-positive cocci (e.g., Streptococci) and some Gram-negative organisms

  • Useful against atypical organisms, lacks anaerobic coverage

• Pharmacokinetics:

  • Erythromycin affected by food; Clarithromycin unaffected

  • Azithromycin has optimal tissue distribution, particularly in macrophages

  • Varies with half-lives (6 hours for Erythromycin, >24 hours for Azithromycin)

• Clinical Uses:

  • Streptococcal throat infections (in penicillin-allergic patients)

  • Community-acquired pneumonia (CAP); combined with beta-lactams to counter resistant strains

  • Clarithromycin in H. pylori eradication

• Adverse Reactions:

  • Gastrointestinal disturbances

  • QT interval prolongation

AMINOGLYCOSIDES

• Properties:

  • Bactericidal

  • Protein synthesis inhibitors

• Mechanism of Action:

  • Inhibit bacterial protein synthesis via ribosomal interference

• Pharmacokinetics:

  • Polar compounds; not effectively absorbed orally; administered IV for systemic effect

  • Dosage adjustment is necessary for renal insufficiency

• Adverse Effects:

  • Ototoxicity (auditory and vestibular damage, especially in renal impairment)

  • Nephrotoxicity, more common in elderly

LINEZOLID

• Spectrum:

  • Effective against all Gram-positive cocci, including MRSA and VRSA

• Uses:

  • Used in MRSA infections

LINCOSAMIDES

• Example:

  • Clindamycin

• Properties:

  • Broad-spectrum bacteriostatic antibiotic that targets both aerobic and anaerobic pathogens

• Clinical Uses:

  • Particularly useful for patients allergic to beta-lactams; better efficacy in resistant infections

• Adverse Effects:

  • Nausea, vomiting, diarrhea, jaundice, agranulocytosis, and risk of pseudomembranous colitis

FLUOROQUINOLONES

• Classification:

  • Divided into first, second, third, and fourth generations based on antimicrobial activity

• Therapeutic Uses:

  • Bactericidal, effective against gram-negative infections resistant to other antibiotics

  • Moxifloxacin particularly effective in odontogenic and periodontal infections

• Adverse Effects:

  • CNS: headaches, dizziness

  • GIT: nausea, diarrhea

  • Musculoskeletal: tendonitis and tendon rupture

METRONIDAZOLE

• Spectrum:

  • Active against anaerobes and effective for Clostridium difficile infections

• Adverse Reactions:

  • Gastrointestinal issues, metallic taste, potential for seizures

• Drug Interactions:

  • Caution with other drugs that prolong QT intervals; interacts with warfarin

ANTIFUNGAL DRUGS

• Classification:

  • Systemic or topical agents

• Nystatin:

  • Indicated for Candida infections, used topically

• Amphotericin B:

  • IV administration for systemic infections, known for nephrotoxicity

ANTIVIRAL DRUGS

• Common Oral Viral Infections:

  • Herpes, Epstein-Barr, varicella-zoster, Coxsackie, HPV, HIV

• Acyclovir:

  • Mechanism: Competitive substrate for DNA polymerase; indicates prophylaxis against herpetic infections

• Adverse Effects of Acyclovir:

  • Nausea, headaches, potential nephrotoxicity, hepatotoxicity