Arcanobacterium species

Paul G. Auwaerter, M.D.
Arcanobacterium species is a topic covered in the Johns Hopkins ABX Guide.

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  • Arcanobacterium haemolyticum: Agent mostly causes pharyngitis or soft tissue infections.
    • The major human pathogen in this group.
    • Gram-positive facultative anaerobe bacillus, not thought to be part of routine human oral or skin flora.
      • Organisms are thin, curved and may have rudimentary branching.
      • β-hemolytic, need to evaluate when catalase-negative and no Lancefield group antigens found (which would indicate non-streptococcal origin).
        • Growth improved on blood-enriched media, 37ºC with 5-10% CO2.
        • Hemolysis best observed on human or horse blood in a CO2-enriched atmosphere.
          • Frequently overlooked on plates with commensal oral flora.
      • Sometimes Gram variable on staining.
      • Formerly called Corynebacterium hæmolyticum.
  • Other Arcanobacterium spp. may occasionally cause human infection.
    • A. pyogenes: mostly an animal pathogen as a major cause of mastitis in livestock, but an occasional cause of human infection including soft tissues and other sites. Most often described in rural environs.
    • A. bernardiae: non-branching on Gram stain. Rare occurrences described causing bacteremia, musculoskeletal and eye infections.
  • Trueperella bernardiae: previously transferred to the Arcanobcaterium genus, but now reclassified. A rare cause of human infection (wound, bloodstream, joint, renal).
    • Considered part of normal skin and oral flora.
    • Also frequently not identified as listed as a Corynebacterium spp.

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Last updated: May 5, 2019