Gram-negative anaerobes and some of the infections they cause include Bacteroides (most common): Intra-abdominal infections Fusobacterium: Abscesses, wound infections, and pulmonary and intracranial infections Porphyromonas: Aspiration pneumonia and periodontitis Prevotella: Intra-abdominal, dental, gynecologic, and soft-tissue infections Gram-positive anaerobes and some of the infections they cause include Actinomyces: Head, neck, abdominal, bone, and pelvic infections and aspiration pneumonia (actinomycosis) Clostridia: Intra-abdominal infections (eg, clostridial necrotizing enteritis), soft-tissue infections, and gas gangrene due to C perfringens; food poisoning due to C perfringens type A; botulism and infant botulism due to C botulinum; tetanus due to C tetani; and Clostridioides (formerly Clostridium) difficile-induced colitis and diarrhea (pseudomembranous colitis) Peptostreptococcus and Finegoldia (formerly Peptostreptococcus magnus): Oral, respiratory, bone and joint, soft-tissue, and intra-abdominal infections Cutibacterium (formerly Propionibacterium): Foreign body infections (eg, in a cerebrospinal fluid shunt, prosthetic joint, or cardiac device); acne vulgaris Anaerobic infections are typically suppurative, causing abscess formation and tissue necrosis and sometimes septic thrombophlebitis, gas formation, or both.