Medusa head appearance is a feature of: (A) Bacillus subtilis, (B) Bacillus stearothermophilus, (C) Bacillus cereus, (D) Bacillus anthracis
Answer is D. Bacillus anthracis:When grown on blood agar plates, the organisms produce nonhemolytic gray to white, tenacious colonies with a rough texture and a ground-glass appearance. Comma-shaped outgrowths (Medusa head, "curled hair") may project from the colony.Reference: Jawetz, Melnick, & Adelberg's Medical Microbiology; 27th edition; Chapter 11; Spore-Forming Gram-Positive Bacilli: Bacillus and Clostridium Species