Brain Abscess
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PATHOGENS
- In 80-90% of brain abscesses, multiple organisms are recovered by culture (even more with molecular techniques).
- Bacterial:
- Streptococci most common single organisms identified (30-50%), but anaerobic or other aerobic organisms can predominate.
- Gram negatives are more common in infants.
- Early infection = cerebritis, subsequent necrosis and capsule formation → abscess.
- Causes of pyogenic abscess:
- ~25% unknown source (cryptogenic)
- ~50% related to the contiguous spread of infection
- ~25% hematogenous
- Causes of pyogenic abscess:
- Fungal causes include Candida spp., Aspergillus, Zygomycetes.
- Parasitic causes include protozoa and helminths.
- Source or host specifics:
- Paranasal sinusitis: microaerophilic (S. intermedius group) and anaerobic strep, Haemophilus species, Bacteroides spp, Fusobacterium spp, Prevotella spp.
- Otogenic infection: aerobic and anaerobic streptococci, Enterobacteriaceae, Pseudomonas aeruginosa , Prevotella spp, B. fragilis.
- Odontogenic infection: S. viridans and anaerobic streptococci, Bacteroides spp, Fusobacterium spp, Prevotella spp, Actinomyces spp.
- Endocarditis: Staphylococcus aureus, S. viridans, Enterococcus.
- Lung abscess: microaerophilic and anaerobic streptococci, Actinomyces species, Fusobacterium species, Nocardia species, Prevotella.
- Penetrating trauma: Staphylococcus aureus, aerobic streptococci, Clostridium species, Enterobacteriaceae.
- Postoperative: Staphylococcus epidermidis, S. aureus, Enterobacteriaceae, Pseudomonas aeruginosa.
- Right to left shunt (congenital heart disease): microaerophilic and aerobic streptococci.
- Compromised host (AIDS, cancer chemotherapy, chronic steroids, lymphoma): toxoplasmosis, Nocardia, EBV lymphoma, TB, fungal (Aspergillus or other).
- Solid organ transplant patients: fungal causes = up to 90% of brain abscesses.
- Immigrant: cysticercosis, echinococcus, TB (tuberculoma).
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PATHOGENS
- In 80-90% of brain abscesses, multiple organisms are recovered by culture (even more with molecular techniques).
- Bacterial:
- Streptococci most common single organisms identified (30-50%), but anaerobic or other aerobic organisms can predominate.
- Gram negatives are more common in infants.
- Early infection = cerebritis, subsequent necrosis and capsule formation → abscess.
- Causes of pyogenic abscess:
- ~25% unknown source (cryptogenic)
- ~50% related to the contiguous spread of infection
- ~25% hematogenous
- Causes of pyogenic abscess:
- Fungal causes include Candida spp., Aspergillus, Zygomycetes.
- Parasitic causes include protozoa and helminths.
- Source or host specifics:
- Paranasal sinusitis: microaerophilic (S. intermedius group) and anaerobic strep, Haemophilus species, Bacteroides spp, Fusobacterium spp, Prevotella spp.
- Otogenic infection: aerobic and anaerobic streptococci, Enterobacteriaceae, Pseudomonas aeruginosa , Prevotella spp, B. fragilis.
- Odontogenic infection: S. viridans and anaerobic streptococci, Bacteroides spp, Fusobacterium spp, Prevotella spp, Actinomyces spp.
- Endocarditis: Staphylococcus aureus, S. viridans, Enterococcus.
- Lung abscess: microaerophilic and anaerobic streptococci, Actinomyces species, Fusobacterium species, Nocardia species, Prevotella.
- Penetrating trauma: Staphylococcus aureus, aerobic streptococci, Clostridium species, Enterobacteriaceae.
- Postoperative: Staphylococcus epidermidis, S. aureus, Enterobacteriaceae, Pseudomonas aeruginosa.
- Right to left shunt (congenital heart disease): microaerophilic and aerobic streptococci.
- Compromised host (AIDS, cancer chemotherapy, chronic steroids, lymphoma): toxoplasmosis, Nocardia, EBV lymphoma, TB, fungal (Aspergillus or other).
- Solid organ transplant patients: fungal causes = up to 90% of brain abscesses.
- Immigrant: cysticercosis, echinococcus, TB (tuberculoma).
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