Clindamycin Spectrum of Activity
Clindamycin is a bacteriostatic antibiotic with excellent activity against anaerobic bacteria, gram-positive aerobes including Staphylococcus aureus and streptococci, but has no activity against most gram-negative aerobic bacteria. 1
Mechanism of Action
- Inhibits bacterial protein synthesis by binding to the 23S RNA of the 50S ribosomal subunit
- Bacteriostatic rather than bactericidal
- Half-life of 2-3 hours in normal adults, allowing for dosing every 6-8 hours 1
Spectrum of Activity
Effective Against:
Gram-positive Aerobes:
- Staphylococcus aureus (methicillin-susceptible strains)
- Staphylococcus epidermidis (methicillin-susceptible strains)
- Streptococcus pneumoniae (penicillin-susceptible strains)
- Streptococcus pyogenes (Group A strep)
- Streptococcus agalactiae (Group B strep)
- Other streptococci (Groups C, G, and viridans group) 2, 1
Anaerobic Bacteria:
- Clostridium perfringens
- Clostridium clostridioforme
- Fusobacterium necrophorum
- Fusobacterium nucleatum
- Peptostreptococcus anaerobius
- Prevotella melaninogenica
- Prevotella bivia
- Prevotella intermedia
- Actinomyces israelii
- Cutibacterium acnes (formerly Propionibacterium acnes) 1
Protozoal Activity:
- Some activity against Toxoplasma gondii
- Some activity against Plasmodium falciparum 3
Not Effective Against:
- Most gram-negative aerobic bacteria (including Escherichia coli)
- Enterococci species
- Pseudomonas aeruginosa 1, 4
Clinical Applications
Based on its spectrum, clindamycin is particularly useful for:
Skin and soft tissue infections - Especially those caused by S. aureus (including some MRSA) and streptococci 5
Mixed aerobic/anaerobic infections - Particularly when combined with antibiotics active against gram-negative organisms 5
Anaerobic infections - Including those caused by Bacteroides species 4
Gynecological infections - Effective for pelvic inflammatory disease, endometritis, and tubo-ovarian abscesses (often combined with an aminoglycoside) 2, 6
Diabetic foot infections - Useful as part of combination therapy 5
Animal and human bite wounds - Has good activity against oral flora including anaerobes 5
Important Considerations
Resistance Concerns:
- Increasing clindamycin resistance among S. aureus isolates
- Inducible clindamycin resistance - D-zone testing is recommended before using for serious MRSA infections 7
- Cross-resistance with macrolides and streptogramin B antibiotics 1
Adverse Effects:
- Clostridioides difficile-associated diarrhea (pseudomembranous colitis) is the most significant adverse effect 4
- Gastrointestinal side effects are common 6
Dosing Considerations
- For serious infections: 600-900 mg IV every 8 hours
- For mild to moderate infections: 300-450 mg PO every 6-8 hours 5
- Dose adjustments may be needed in severe hepatic impairment but not in renal impairment 1
Clindamycin's unique spectrum makes it particularly valuable for polymicrobial infections involving both gram-positive cocci and anaerobes, but its use should be balanced against the risk of C. difficile infection and increasing resistance patterns.