Notes on Clindamycin vs Metronidazole

Jul 30, 2024

Clindamycin vs Metronidazole in Anaerobic Bacterial Infections

Introduction

  • Discussion on clinical decisions for anaerobic bacterial infections.
  • Importance of knowing when to use Clindamycin vs. Metronidazole.

Clinical Sayings

  • Above Diaphragm: Prefer Clindamycin.
  • Below Diaphragm: Prefer Metronidazole.

Questions to Address

  1. Why does Metronidazole fail above the diaphragm?
  2. Why is Metronidazole successful below the diaphragm?
  3. Why is Clindamycin successful above the diaphragm?
  4. Why does Clindamycin fail below the diaphragm?

Microbiology Insights

Differences in Microbiota

  • Above Diaphragm: Derived from Oro-facial and oral microbiota.
  • Below Diaphragm: Various sources including gut flora.

Important Anaerobic Bacteria

Anaerobic Gram-Negative Rods

  1. Bacteroides (important - especially B. fragilis):
    • Found below the diaphragm.
  2. Prevotella
  3. Porphyromonas
  4. Fusobacterium

Mnemonic: "Naughty Boy Places Pink Flower in Virgins' Hair".

Anaerobic Gram-Positive Rods

  • Clostridia (Clostridium species)
  • Lactobacillus
  • Actinomyces (now Actinomyces)
  • Propionibacterium (now Cutibacterium)
  • Peptostreptococcus

Mnemonic: "CLAP (Clostridia, Lactobacillus, Actinomyces, Peptostreptococcus)".

Key Points on Infections

  • Most anaerobic infections are polymicrobial.
  • Sources of anaerobic bacteria include normal microbiota, especially in mucosal surfaces.
  • Oro-facial microbiota is a significant source for infections above the diaphragm.

Special Note on Bacteroides

  • B. fragilis is important below the diaphragm.
  • Distinction between Bacteroides fragilis and Bacteroides non-fragilis (the latter found in the oral cavity).

Infections Above the Diaphragm

  • Predominantly from oral microbiota.
  • Infections include:
    • Oro-dental infections.
    • Oro-facial infections.
    • Deep neck infections.
    • Brain abscesses via aspiration.
    • Aspiration pneumonia.

Infections Below the Diaphragm

  • More diverse with mixed populations of bacteria.

Conclusion

  • Understanding the sources and characteristics of anaerobic bacteria helps in determining the appropriate antibiotic therapy for infections above or below the diaphragm.