Spore forming anaerobic bacteria that causes gas gangrene C perfringens is the most common etiologic agent that causes gas gangrene. Clostridia species. anthracis causes anthrax through its toxin and spores. Note which of the following classifications apply to each microbe: Gram negative (G-) or Gram positive (G+); acid-fast bacillus positive (AFB+); spore-forming bacteria (SFB); anaerobic (AN) or aerobic (A); and cocci shape (CS), bacillus shape (BS), cluster (CL), or ochain (CH). Streptococcus pyogenes c. perfringens is a pathogenic, spore-forming, anaerobic bacterium that can cause gas gangrene, food poisoning, and necrotizing enteritis by producing various toxins. Clostridial myonecrosis historically was a common war wound infection with an incidence of 5%. b. [2] Myonecrosis is a condition of necrotic damage, specific to Gas gangrene, or clostridial myonecrosis, is an example of a monomicrobial necrotizing infection caused by Clostridium spp. ambient air (95% O2 and 5% CO2).