Bacteroides

Taxobox
color = lightgrey
name = "Bacteroides"

---

image_width = 240px
image_caption = "Bacteroides" spp. anaerobically cultured in blood agar medium.
regnum = Bacteria
phylum = Bacteroidetes
classis = Bacteroidetes
ordo = Bacteroidales
familia = Bacteroidaceae
genus = "Bacteroides"
genus_authority = Castellani & Chalmers 1919
subdivision_ranks = Species
subdivision ="B. acidifaciens"
"B. distasonis" (reclassified as "Parabacteroides distasonis")
"B. gracilis"
"B. fragilis"
"B. oris"
"B. ovatus"
"B. putredinis"
"B. pyogenes"
"B. stercoris"
"B. suis"
"B. tectus"
"B. thetaiotaomicron"
"B. vulgatus"
etc.

"Bacteroides" is a genus of Gram-negative, bacillis bacteria. "Bacteroides" species are non-endospore-forming, anaerobes, and may be either motile or non-motile, depending on the species. [cite book | author = Madigan M, Martinko J (editors). | title = Brock Biology of Microorganisms | edition = 11th ed.
publisher = Prentice Hall | year = 2005 | isbn = 0-13-144329-1 ] The DNA base composition is 40-48% GC. Unusual in bacterial organisms, "Bacteroides" membranes contain sphingolipids. They also contain meso-diaminopimelic acid in their peptidoglycan layer.

"Bacteroides" are normally mutualistic, making up the most substantial portion of the mammalian gastrointestinal flora,cite book | author = Dorland WAN (editor) | title = Dorland's Illustrated Medical Dictionary| edition = 30th| publisher = W.B. Saunders| year = 2003| id = ISBN 0-7216-0146-4] where they play a fundamental role in processing of complex molecules to simpler ones in the host intestine. As many as 10¹⁰-10¹¹ cells per gram of human feces have been reported. [cite book | author = Finegold SM, Sutter VL, Mathisen GE| title = Normal indigenous intestinal flora (pp. 3-31) in Human intestinal microflora in health and disease. | edition = | publisher = Academic Press| year = 1983| isbn = 0-12-341280-3] They can use simple sugars when available, but the main source of energy is polysaccharides from plant sources.

Pathogenesis

"Bacteroides" species also benefit their host by excluding potential pathogens from colonizing the gut. Some species ("B. fragilis", for example) are opportunistic human pathogens, causing infections of the peritoneal cavity, gastrointestinal surgery, and appendicitis via abscess formation, inhibiting phagocytosis, and inactivating beta-lactam antibiotics.cite book | author = Ryan KJ, Ray CG (editors) | title = Sherris Medical Microbiology | edition = 4th ed. | publisher = McGraw Hill | year = 2004 | isbn = 0-8385-8529-9 ] Although "Bacteroides" species are anaerobic, they are aerotolerant and thus can survive in the abdominal cavity.

In general, "Bacteroides" are resistant to a wide variety of antibiotics — β-lactams, aminoglycosides, and recently many species have acquired resistance to erythromycin and tetracycline. This high level of antibiotic resistance has prompted concerns that "Bacteroides" species may become a reservoir for resistance in other, more highly-pathogenic bacterial strains.cite journal | author=Salyers AA, Gupta A, Wang Y | title=Human intestinal bacteria as reservoirs for antibiotic resistance genes | journal=Trends Microbiol | year=2004 | pages=412–6 | volume=12 | issue=9 | pmid = 15337162 | issn = 0966-842X | doi=10.1016/j.tim.2004.07.004]

"B. fragilis"

"Bacteroides fragilis" is an obligate anaerobe of the gut. It is involved in 90% of anaerobic peritoneal infections.Fact|date=February 2007 In general, "B. fragilis" is susceptible to metronidazole, carbapenems, beta-lactam/beta-lactamase inhibitor combinations (e.g., Unasyn, Zosyn), and certain antimicrobials of the cephamycin class, including cefoxitin. The bacteria have inherent high-level resistance to penicillin. Clindamycin is no longer recommended as the first-line agent for "B. fragilis" due to emerging high-level resistance (>30% in some reports).cite book|author=Mandell GL, Bennett JE, Dolin R|title=Principles and Practice of Infectious Diseases|edition=6th ed.|publisher=Churchill Livingstone|year=2004|isbn = 0443066434] Bacteriophages infecting "B. fragilis" are commonly used as tracers of human faecal material; see work undertaken by the University of Barcelona and EPHRU (Environment and Public Health Research Unit) at the University of Brighton.

Polysaccharide A (PSA) from this bacteria is reported to be involved in the protection of experimental colitis induced by "Helicobacter hepaticus". [ [http://www.nature.com/nature/journal/v453/n7195/abs/nature07008.html A microbial symbiosis factor prevents intestinal inflammatory disease] ]

References

ee also

* Flavobacterium
* Cytophaga

External links

* [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=Books&cmd=Search&term=bacteroides+AND+mmed%5Bbook%5D&doptcmdl=TOCView "Bacteroides" references] in Baron's "Medical Microbiology" (online at the NCBI [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=books bookshelf] ).
* [http://borg.med.ecu.edu/~webpage/about.html "Bacteriodes"] in detail.