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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.
- Based on 16S rRNA sequencing, organism distinguished from Corynebacterium spp.
- 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.