Bacteroides and Prevotella organisms from the oral cavity can cause chronic sinusitis, chronic otitis media, dental infection, peritonsillar abscess, cervical adenitis, retropharyngeal space infection, aspiration pneumonia, lung abscess, empyema, or necrotizing pneumonia. Species from the gastrointestinal tract are recovered in patients with peritonitis, intra-abdominal abscess, pelvic inflammatory disease, postoperative wound infection, or vulvovaginal and perianal infections. Soft tissue infections include synergistic bacterial gangrene and necrotizing fasciitis. Invasion of the bloodstream from the oral cavity or intestinal tract can lead to brain abscess, meningitis, endocarditis, arthritis, or osteomyelitis. Skin involvement includes omphalitis in newborn infants, cellulitis at the site of fetal monitors, human bite wounds, infection of burns adjacent to the mouth or rectum, and decubitus ulcers. Neonatal infections, such as conjunctivitis, pneumonia, bacteremia, or meningitis, rarely occur. Most Bacteroides infections are polymicrobial.