Not always a commensal: A case of mastitis by Corynebacterium amycolatum

Gram positive rods seen on Gram's stain are often dismissed as skin commensal organisms. Diphtheroids (Non-diphtherial Corynebacterium species), as they are collectively called, are taken as harmless bystanders in a skin and soft tissue infection (SSTI). However, emerging evidence has established virulence factors in some of these species leading to various infections. Here, we describe a case of mastitis in a 43 year old female caused by Corynebacterium amycolatum. The organism was seen as thick Gram positive rods on Gram stain and was isolated as a pure growth on Blood agar. Identification was done on Vitek-2 and confirmed by matrix assisted laser desorption-ionization - Time-offlight (MALDI-TOF). Patient was managed successfully with surgical excision and antibiotics.