Anaerobic Infections

Excerpt

Anaerobic bacteria are part of the normal flora of human skin and mucosal membranes. The site of anaerobic infection is commonly the site of normal colonization. The spectrum of infections ranges from local abscesses to life-threatening infections. Anaerobic bacteria differ from aerobic bacteria in their oxygen requirement. Oxygen is toxic to anaerobes which can be explained by the absence of enzymes in the anaerobes of catalase, superoxide dismutase, and peroxidase enzymes. Anaerobes are fastidious organisms and are difficult to grow if proper collection and culture methods are not used. The diagnosis requires clinical suspicion and proper microbiological identification.

Based on oxygen requirement, bacteria can be divided into the following groups:

Obligate aerobes require oxygen as a terminal electron acceptor and do not have any other source of energy, such as fermentation.

Obligate anaerobes obtain energy through fermentation and use organic compounds as a terminal electron acceptor.

Facultative anaerobes can grow in the presence or absence of oxygen.

The obligate anaerobes can further be subdivided into 2 types based on a percentage of oxygen that can prove toxic. Strict obligate anaerobes will not survive if there is more than half a percent oxygen in the environment, while moderate obligate anaerobes can still grow in a 2 to 8% oxygen environment.