Polypeptides, glycopepetides, rifamycin

Question 1

Glycopepetides : overview

Answer 1

• PEPTIDOGLYCAN synthesis inhibition
• inhibit the cell wall structure Gram +ve cocci
• BACTERIOCIDAL in most bacteria , BACTERIOSTATIC in enterococci
• Vancomycin and teicoplanin inhibit transgltcosidase and are extremely toxic , therefore are used in critically ill or B-lactams hypersensitive patients
• narrow spectrum: Gram positive rods and cocci (Gram negative rods is resistant)
• don’t penetrate CSF
• last resort antibiotics in acute bacterial skin by staph + strep

Question 2

Glycopepetides: Side Effect

Answer 2

1. Telcoplanin
2. Vancomycin: IV ,pain in inj site, can cause tissue necrosis, nephrotoxicity,
   * vancomycin derivatives: oritavancin, dalbavancin, and telavancin (longer HL)
3. Rifamycin, Rifabutin: semisynthetic, prophylaxis of meningococcal disease, TB , mycobacteriosis

Question 3

Glycopepetides: Rifampin

Answer 3

• RNA synthesis inhibitor: inhibits bacterial DNA-dependent RNA polymerase by binding to the β subunit of the polymerase.
• high selectivity for bacteria polymerase
• SE (unusual): , nausea, vomiting, Jaundice and dermatitis
• gets to CSF
• G+, rhodoccocus eq., Neisseria sp. , mycobacteria
• meningitis prophylaxis
• liver microsomal enzymes and enhances the metabolism of other drugs such as anticoagulants, contraceptives, and corticosteroids

Question 4

Glycopepetides: Mupirocin

Answer 4

• Bacteriostatic, Reversibly inhibits the isoleucyl tRNA synthetase enzyme. *Usage ONLY TOPICALLY against S. aureus infections
• intranasal use against MRSA strains

Question 5

Glycopepetides: Polymyxin

Answer 5

• acts as a detergent to disrupt the cell membrane of Gram negative mostly.
• Cationic basic polypeptides (detergent): rapid killing but effect all membrane similarly
• concentration dependent bactericidal.
• poorly absorbed and distributed
• positively charged molecules attracted to negatively charged bacteria (LPS).
• act synergistically when combined with potentiated sulfonamides, tetracyclines, and some other antibacterial (penicillin’s, fluoroquinolones and aminoglycosides)
• SE: tubular necrosis and neurotoxic
• IV is toxic

Question 6

Glycopepetides: Side effect

Answer 6

• Crystalluria, haematuria, crystal nephrosis
• heptatotoxicity (rare)
• allergy (doberman)
• KCS
• Dysbacteriosis
• Hypothyroidism