Humans are aerobic organisms if so why do you worry about being infected by an anaerobic organism?

Answer 1

The fact that most of the human normal flora is composed of anaerobic bacteria suggests that anaerobic infections might be of medical concern. Indeed, anaerobic infections can occur in a variety of body sites and involve many different genera. Most of the normal anaerobic flora are not overtly pathogenic; rather, they are considered to be opportunistic. That is, if given the opportunity, they can inflict serious and occasionally life-threatening disease. These types of infections most often occur due to trauma, injury or surgery. In general, a loss of natural barriers that introduce these bacteria into normally sterile body sites may result in infection. The sites commonly involved in anaerobic infection include the following:

1. intraabdominal infections

2. pulmonary infections

3. pelvic infections

4. brain abscesses

5. skin and soft tissue

6. oral and dental infections

7. bacteremia and endocarditis

Treatment of these infections can sometimes be difficult but, generally, moderate to broad spectrum antibiotics are usually effective

http://www.cehs.siu.edu/fix/medmicro/anaer.htm