Infections caused by anaerobic bacteria occur in all parts of body. These infected tissues usually contain a mixture of several kinds of anaerobes and frequently also contain aerobic and facultative bacteria. The types of infection commonly produced by anaerobic bacteria are as follows: 

Intra-abdominal infections:

Abscesses, post operative wound infections and generalized peritonitis produced by anerobes occur as a consequence of bowel perforation during surgery or injury.

Pulmonary infections:

Anaerobic lung infections may originate in the bronchi or the blood. Aspirations from upper respiratory tract that contain large numbers of anaerobic bacteria are responsible for initiating infection in the bronchi.

Pelvic infections:

Anaerobic infections of vagina and uterus sometimes occura after gynecologic surgery or in association with malignancy of pelvic organs.

Brain abscesses:

Anaerobes infrequently produce meningitis, but are a common cause of brain abscesses. The infecting organisms usually originate in the upper respiratory tract.

Skin and soft tissue infections:

Combinations of anaerobes, aerobes and facultative organisms often act synergistically to produce these infections.

Oral and dental infections:

These local infections frequently extend to the face and neck and sometimes to the other parts of the body such as brain.

Bacteremia and endocarditis: 

Anaerobic bacteremia may follow disturbance in an area of the body where an established flora or an infection exists. Endocarditis, an inflammation of the endothelial lining of the heart valve cavities, is occasionally caused by anaerobic Streptococci. 

• Foul-smelling discharge

• Infection proximal to mucosal surface

• Gas in tissues

• Extensive tissue necrosis

• Abscess formation

• Absence of growth in routine aerobic culture (in resource poor countries where anaerobic culture is unavailable)