Published: February 25th, 2015
Revised: July 27th, 2016
Bacteroides is a genus of gram-negative, obligate anaerobes that live symbiotically within mammalian gastrointestinal tracts. Species of Bacteroides are present in huge quantities in human feces and do not persist for very long outside of the gut. Their relationship with the guts of different mammalian hosts are so well defined, you can determine the type of mammalian feces by the species of Bacteroides present.
Bacteroides has become a fecal indicator of choice for assessing sewage contamination in the indoor environment. Not only are members of the genus more reliably present than coliforms in events of sewage contamination, but the obligate anerobic nature of these bacteria (unlike coliforms) mean they cannot replicate in the environment thereby reducing the potential for false positive results.