Lincosamides and Glycopeptides: Mechanisms, Uses, and Resistance

Introduction

Lincosamides are a class of antibiotics primarily effective against Gram-positive bacteria and some anaerobes. Clindamycin is the most commonly used lincosamide.

Mechanism of Action

Lincosamides inhibit bacterial protein synthesis by binding to the 50S ribosomal subunit, preventing the formation of the initiation complex and interfering with peptide chain elongation.

Mechanism of Resistance

• Modification of the ribosomal target site, leading to reduced binding affinity.
• Efflux pumps that pump the drug out of the cell.
• Enzymatic inactivation by bacterial enzymes.

Therapeutic Uses

• Soft tissue infections, bone infections, and anaerobic infections.
• Used in combination for MRSA infections.

Adverse Effects

• Gastrointestinal disturbances (nausea, vomiting, diarrhea).
• Risk of C. difficile-associated diarrhea.
• Rash, blood dyscrasias, and hepatic dysfunction.

Contraindications

• Hypersensitivity to clindamycin.
• History of C. difficile colitis.

Introduction

Glycopeptides are antibiotics primarily used for Gram-positive bacterial infections, especially those resistant to other drugs. Vancomycin is the most commonly used glycopeptide.

Mechanism of Action

Glycopeptides inhibit bacterial cell wall synthesis by binding to the D-alanyl-D-alanine terminal of peptidoglycan precursors, preventing the formation of cross-links in the cell wall.

Mechanism of Resistance

• Modification of the D-alanine-D-alanine target to D-alanine-D-lactate.
• Vancomycin-intermediate *Staphylococcus aureus* (VISA) and Vancomycin-resistant *Enterococcus* (VRE).

Therapeutic Uses

• Severe Gram-positive infections, including MRSA and *Enterococcus* infections.
• Clostridium difficile colitis (oral vancomycin).

Adverse Effects

• Red man syndrome (flushing, rash, hypotension).
• Nephrotoxicity and ototoxicity (with high doses).
• Thrombophlebitis at the injection site.

Contraindications

• Hypersensitivity to vancomycin.
• Renal impairment (dose adjustments required).