From the Guidelines
Brain abscesses are typically caused by bacterial, fungal, or parasitic pathogens, with the most common being Streptococcus species, Staphylococcus aureus, anaerobes, and Enterobacteriaceae, as reported in a recent study 1. The pathogens that cause brain abscesses can vary depending on the population and underlying conditions. In general, the most frequent causative pathogens in community-acquired brain abscess are oral cavity bacteria such as Streptococcus anginosus group, Fusobacterium spp., and Aggregatibacter spp. 1. Other less common aetiologies include Staphylococcus aureus and Gram-negative bacilli in post-neurosurgical brain abscess, Mycobacterium tuberculosis in endemic areas, and Nocardia spp., fungi, and parasites in the severely immune-compromised 1. Some of the key pathogens that can cause brain abscess include:
- Bacterial pathogens:
- Streptococcus species (especially viridans streptococci and Streptococcus pneumoniae)
- Staphylococcus aureus
- Anaerobes (Bacteroides, Prevotella, Fusobacterium)
- Enterobacteriaceae (like Escherichia coli, Klebsiella)
- Fungal pathogens:
- Aspergillus species
- Candida
- Cryptococcus
- Mucormycosis
- Parasitic causes:
- Toxoplasma gondii (especially in HIV patients)
- Taenia solium (neurocysticercosis)
- Entamoeba histolytica It is essential to note that the distribution of causative pathogens can vary depending on the population and underlying conditions, and empiric therapy should be guided by the most likely pathogens and their antimicrobial susceptibilities, as recommended by the European Society of Clinical Microbiology and Infectious Diseases guidelines 1. The treatment of brain abscess typically involves surgical drainage when possible, combined with targeted antimicrobial therapy based on culture results, with regimens lasting 4-8 weeks, and empiric therapy often includes a third-generation cephalosporin plus metronidazole, with vancomycin added if Staphylococcus is suspected 1. Early identification and treatment are crucial to prevent permanent neurological damage. The choice of empirical antimicrobial treatment should be based on the distribution of causative pathogens, their antimicrobial susceptibilities, and pharmacokinetic considerations, as recommended by the guideline panel 1. A recent Danish cohort study confirmed that oral cavity bacteria were the predominant aetiology, accounting for 59% of cases, followed by S. aureus in 6% of cases, and other pathogens with frequencies ranging from 1% to 3% 1. The guideline panel relied on these distributions of causative pathogens, their antimicrobial susceptibilities, and pharmacokinetic considerations for recommendations on optimal empirical antimicrobial treatment 1.
From the FDA Drug Label
Central Nervous System (CNS) Infections, including meningitis and brain abscess, caused by Bacteroides species including the B. fragilis group. The pathogens that can cause Brain Abscess include Bacteroides species, specifically the B. fragilis group 2.
- Key pathogens:
- Bacteroides species
- B. fragilis group Note that the label does not provide an exhaustive list of all possible pathogens that can cause brain abscess, but rather those that are susceptible to metronidazole.