Three cases of Arcanobacterium pyogenes-associated soft tissue infection.

Arcanobacterium pyogenes is an established but often unrecognized human pathogen. A. pyogenes may also be misidentified as Arcanobacterium haemolyticum, which gives remarkably similar results in conventional biochemical tests. In this study, we have reported three cases of wound infections associated with A. pyogenes and also on the bacteriological characteristics which are relevant for identification of these isolates. The negative reverse CAMP test, the ability to produce acid from xylose and to hydrolyse gelatin and the positive beta-glucuronidase test clearly differentiated A. pyogenes from other closely related species. All three isolates were uniformly susceptible to penicillin, ampicillin, amoxicillin-clavulanic acid, ceftriaxone and gentamicin, variably susceptible to tetracycline and erythromycin and uniformly resistant to cotrimoxazole. Only a few confirmed cases have been reported throughout the world and therefore the diagnostic evaluation of this organism is emphasized.