Aggregatibacter species is a topic covered in the Johns Hopkins Antibiotic (ABX) Guide.

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  • Aggregatibacterspp. are normal residents of human oropharyngeal flora (especially dental plaques and gingiva), sometimes urogenital flora. Member of Pasteurellaceae family.
  • Aggregatibacter actinomycetemcomitans (Aa) is a facultative Gram-negative, slowly growing coccobacillus.
    • Formerly known as Actinobacillus actinomycetemcomitans, member of HACEK group. Earlier literature called the organism Haemophilus actinomycetemcomitans.
    • Original name due to descriptions of infections with actinomycotic-like presentations.
      • When isolated in an abscess, almost always found in conjunction with Actinomyces spp.
    • Generally easily isolated, but a slow grower and may need > 7d incubation.
    • Most common cause of Aggregatibacter endocarditis.
  • A. aphrophilus: formerly Haemophilus aphrophilus, is second most common cause of Aggregatibacter endocarditis. Most common in this group to be a cause of brain abscess.
  • A. paraphrophilus: formerly Haemophilus paraphrophilus, less common cause of endocarditis of this species (usually mitral valve), may also cause brain abscess. Also found in GI tract.
  • A. segnis: uncommon commensal in the oropharynx, rare cause of endocarditis, bacteremia.
  • A. urae: meningitis reported.

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Last updated: February 2, 2017