Strictly anaerobic microorganisms cannot grow in the presence of oxygen.  They require special culture in the laboratory for use in tests.

Propionibacterium acnes

Structure and Physiology

This bacteria is a Gram-positive, rod shaped, aerotolerant anaerobe. Slow growing and aerotolerant, this microorganism is part of the normal flora of healthy human skin, living deep inside pores and follicles. 

Clostridium difficile

Structure and Physiology

This bacteria is a Gram-positive, rod shaped, endospore generating obligate anaerobe. Clostridium species are part of the normal human gut flora that produce spores which are highly resistant to chemical and environmental conditions.

Transmission and Disease

C. difficile is commonly associated with hospital acquired infections and is known to cause antibiotic assisted colitis.