A genus that includes many species of obligate anaerobic, nonsporeforming bacteria (family Bacteroidaceae) containing Gram-negative rods. Both motile and nonmotile species occur; motile cells are peritrichous. Some species ferment carbohydrates and produce combinations of succinic, lactic, acetic, formic, or propionic acid s, sometimes with short-chained alcohols; butyric acid is not a major product. Those species which do not ferment carbohydrates produce from peptone either trace to moderate amounts of succinic, formic, acetic, and lactic acid s or major amounts of acetic and butyric acid s with moderate amounts of alcohols and isovaleric, propionic, and isobutyric acid s. They are part of the normal flora of the intestinal tract and to a lesser degree, the respiratory, and urogenital cavities of humans and animals; many species formerly classified as B. have been reclassified as belonging to the genus Prevotella. Many species can be pathogenic. The type species is B. fragilis. [G. bacterion + eidos, form]
- B. bivius a species usually isolated from urogenital and abdominal infections and linked to pelvic inflammatory disease.
- B. capillosus a bacterial species isolated from human cysts and wounds, the mouth, and feces, and from the intestinal tracts of some animals. Its properties differ from those of most B. species; future reclassification is likely.
- B. corrodens former name for Eikenella corrodens.
- B. disiens SYN: Prevotella disiens.
- B. distasonis bacterial species that is part of the normal human fecal flora; an occasional cause of intraabdominal infections.
- B. fragilis a bacterial species found in human and animal intestinal tracts. Although it represents only about 10–20% of B. species found in the colon, it is the primary species associated with intraabdominal abscesses and other subdiaphragmatic infections in humans, including peritonitis, rectal abscess, abdominal surgical wounds, and urogenital tract infection. Its capsule is capable of inducing abscess formation independently; characteristically, this species produces a β-lactamase that inactivates β-lactam antibiotics such as the penicillin and cephalosporin groups; it is the type species of the genus, B..
- B. furcosus former name of Anaerohabdus furcosis.
- B. melaninogenicus SYN: Prevotella melaninogenica.
- B. nodosus a bacterial species that causes foot rot in sheep and goats; it can be found in the human intestinal tract and has been associated with human infections; this organism has many properties different from other species of B., and its final classification is uncertain. SYN: Dichelobacter nodosus.
- B. oralis former name of Prevotella oralis.
- B. oris former name of Prevotella oris.
- B. pneumosintes former name for Dialister pneumosintes.
- B. praeacutus a species isolated from the intestinal tracts of infants and adults, gangrenous lesions, lung abscesses, and blood. SYN: Tissierella praeacuta.
- B. putredinis a species isolated from feces, cases of acute appendicitis, and abdominal and rectal abscesses; also from foot rot of sheep and from farm soil. Its properties are divergent from most B. species.
- B. splanchnicus a species in the indole positive group, found in normal human colonic flora, and occasionally in human specimens with unique metabolic properties that include production of large amounts of n-butyric acid; it appears to be closely related to the genus Porphyromonas.
- B. thetaiotamicron a bacterial species found in the intestinal tract; second only in its genus to B. fragilis as a cause of human subdiaphragmatic infections.
- B. ureolyticus a species isolated from infections of the respiratory and intestinal tracts, and from the buccal cavity, intestinal tract, urogenital tract, and blood after a dental extraction. It is closely related to Campylobacter species.

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Bac·te·roi·des -'rȯid-(.)ēz n
1) cap a genus of gram-negative anaerobic bacteria that belong to the family Bacteroidaceae, that have rounded ends, produce no endospores and no pigment, and that occur usu. in the normal intestinal flora
2) pl -roides a bacterium of the genus Bacteroides or of a closely related genus

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a genus of Gram-negative, mostly nonmotile, anaerobic rodlike bacteria. They are normally present in the alimentary and urinogenital tracts of mammals and are found in the mouth, particularly in dental plaque associated with periodontal disease. Some species have now been classified into new genera, Porphyromonas and Prevotella.

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Bac·te·roi·des (bak″tər-oiґdēz) [bacterio- + -oid] a genus of gram-negative, anaerobic, non–spore-forming, rod-shaped bacteria of the family Bacteroidaceae, made up of organisms that are nonmotile or motile with peritrichous flagella. They are normal inhabitants of oral, respiratory, intestinal, and urogenital cavities, and may constitute the predominant bacteria of the normal human colon. Some species are potential pathogens, causing abscesses and bacteremias that can be fatal.

Medical dictionary. 2011.

Look at other dictionaries:

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  • Bacteroides — noun type genus of Bacteroidaceae; genus of Gram negative rodlike anaerobic bacteria producing no endospores and no pigment and living in the gut of man and animals • Syn: ↑genus Bacteroides • Hypernyms: ↑bacteria genus • Member Holonyms:… …   Useful english dictionary

  • bacteroides — /bak teuh roy deez/, n., pl. bacteroides. any of several rod shaped, anaerobic bacteria of the genus Bacteroides, occurring in the alimentary and genitourinary tracts of humans and other mammals, certain species of which are pathogenic. [1919; <… …   Universalium

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