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A family of nonmotile, non-spore-forming, anaerobic bacteria (order Eubacteriales) containing gram-positive (staining may be equivocal) cocci, 0.5-1.6 mcm in diameter, which occur singly, in pairs, chains, tetrads, and irregular masses but not in three-dimensional, cubic packets. These organisms are chemoorganotrophic and have complex nutritional requirements. Carbohydrates may or may not be fermented by these organisms, which produce gas, principally CO2 and usually H2, from amino acids, or carbohydrates, or both. They are found in the mouth and in intestinal and respiratory tracts of humans and other animals; they are frequently found in normal and pathologic human female urogenital tracts.
A family of gram-positive, anaerobic cocci that includes the genus Peptococcus and may be normal or pathogenic inhabitants of the upper respiratory and intestinal tracts.