Arcanobacterium haemolyticum

Gram Stain

• Gram positive irregular bacilli (aerobic)

Clinical Significance

This organism may be part of commensal flora of the respiratory and gastrointestinal tracts.

A. haemolyticum is associated with pharyngitis, typically with a rash (erythematous, scarlatiniform, urticarial or morbilliform involving trunk and extremities, sparing face, palms, and soles) in young adults.

It has also been associated with septicemia, septic thrombophlebitis (Lemierre’s syndrome), tonsillar abscesses, pneumonia, empyema, otitis media, sinusitis, ocular infections, peritonitis, chorioamnionitis, endocarditis, brain abscesses, subdural empyema, skin/soft tissue (cellulitis, necrotizing fasciitis, omphalitis, venous ulcers), and bone/joint infections.

Infections are often polymicrobial.

Usual Susceptibility Pattern

This organism is typically susceptible to beta-lactam agents (penicillin/ceftriaxone), clindamycin, macrolides, tetracyclines, and rifampin.

Failure of penicillin has been described and thought to be due to tolerance.  

Doxycycline and minocycline tend to have better activity than tetracycline.

It is resistant to TMP/SMX.

Quinolones and aminoglycosides do not have reliable activity.

Vancomycin resistance (Van A gene) has been reported.