Colon anaerobic bacteria

Ba.cteria., A wide variety of bacteria can colonize cooling systems. Spherical, rod-shaped, spiral, and filamentous forms are common. Some produce spores to survive adverse environmental conditions such as dry periods or high temperatures. Both aerobic bacteria (which thrive in oxygenated waters) and anaerobic bacteria (which are inhibited or killed by oxygen) can be found in cooling systems. 

There is also a segmental distribution of the types of bacteria. Strict anaerobic species are normally confined to the oral cavity and the colon, habitats they densely colonize and predominate [1-5] (fig. 1). Bacteria indigenous to the upper respiratory tract (URT flora) and anaerobic bacteria of oral origin are swallowed with saliva and recovered from the upper gut at densities below 105 CFU/ ml. Under physiological conditions, they are considered transitory rather than indigenous to the upper gut. Facultative anaerobic bacteria are usually confined to the distal small bowel and colon, but transient species entering the gut with nutrients are occasionally recovered from the healthy upper gut at low counts. 

Selective failure of the gastric acid barrier, as seen in otherwise healthy individuals on proton pump inhibitors or with H. pylori-induced corpus gastritis, results in gastric colonization of swallowed oropharyngeal bacteria. In otherwise healthy subjects this will be mainly Gram-positive bacteria belonging to the URT flora and strict anaerobic bacteria of oral origin. 

Nevertheless, a rapid disappearance of resistant bacteria was observed after stopping the antibiotic treatment (fig. 5). Different kinetics of disappearance were, however, observed. The aerobic species showed a more rapid return to the baseline sensitive status whereas the anaerobic bacteria, especially the Gram-negative rods, regained sensitivity to rifaximin more slowly. In any case, 3 months after the end of treatment resistant strains were no longer detectable in the feces [82], These results support the cyclic use of rifaximin that has been adopted by the investigators in the treatment of hepatic encephalopathy [77] and colonic diverticular disease [79]. 

Antibiotics alter the normal colonic flora, leading to loss of colonization resistance, which is the ability of the normal flora to protect against overgrowth of pathogens, especially when the anaerobic flora are depleted [15], In CDAD, the altered colonization resistance can allow for the overgrowth of C. difficile in the colon. The bacteria produces two toxins which cause disease (toxin A, an enterotoxin, and toxin B, a cytotoxin). The toxins of C. difficile inactivate Rho proteins, which results in the loss of cytoskeletal integrity in enterocytes. Cellular damage results in fluid loss, exudation and diarrhea. The most severe form of C. difficile diarrhea is pseudomembranous colitis, which can cause severe colitis, toxic colon and rarely colon perforation and death. 

Botulinum exotoxin impedes release of neurotransmitter vesicles from cholinergic terminals at neuromuscular junctions. Botulinum exotoxin is ingested with food or, in infants, synthesized in situ by anaerobic bacteria that colonize the gut. A characteristic feature of botulinum paralysis is that the maximal force of muscle contraction increases when motor nerve electrical stimulation is repeated at low frequency, a phenomenon attributable to the recruitment of additional cholinergic vesicles with repetitive depolarization of neuromuscular presynaptic terminals. Local administration of Clostridium botulinum exotoxin is now in vogue for its cosmetic effects and is used for relief of spasticity in dystonia and cerebral palsy [21]. 

Most pressure sores are colonized by bacteria however, bacteria frequently infect healthy tissue. A large variety of aerobic gram-positive and gramnegative bacteria, as well as anaerobes, are frequently isolated. 

Leclerc M, BemaUer A, DonadiUe G, Lelait M. 1997. H2/CO2 metabolism in aceto-genic bacteria isolated from the human colon. Anaerobe 3 307-15. 

Thomas LA, Veysey MJ, Murphy GM, Russell-Jones D, French GL, Wass JAH, Dowling RH. Octreotide induced prolongation of colonic transit increases fecal anaerobic bacteria, bile acid metabolizing enzymes, and serum deoxy-cholic acid in patients with acromegaly. Gut 2005 54 630-5. 

Anaerobic bacteria in the colon produce significant quantities of methanethiol along with hydrogen sulfide. Rodent studies indicate that these substances are detoxified to thiosulfate by the action of a specialized detoxification system that operates in the mucous layer of the colon lining.2 The failure of this system may contribute to some diseases of the colon, such as ulcerative colitis. 

The large intestine extends from the ileocecal valve to the anus. It is wider than the small intestine except for the descending colon, which when empty may have the same diameter as the small intestine. Major functions of the colon are absorption of water, Na+, and other electrolytes, as well as temporary storage of excreta followed by their elimination. The colon harbors large numbers of mostly anaerobic bacteria that can cause disease if they invade tissues. These bacteria metabolize carbohydrates to lactate, short-chain fatty acids (acetate, propionate, and butyrate), and gases (CO2, CH4, and H2). Ammonia, a toxic waste product, is produced from urea and other nitrogenous compounds. Other toxic substances are also produced in the colon. Ammonia and amines (aromatic or aliphatic) are absorbed and transported to the liver via the portal blood, where the former is converted to urea (Chapter 17) and the latter is detoxified. The liver thus protects the rest of the body from toxic substances produced in the colon. Colonic bacteria can also be a source of certain vitamins (e.g., vitamin K, Chapter 36). 

This unusual form of lactic acidosis is due to increased production and accumulation of D-lactate in circulation. The normal isomer synthesized in the human body is L-lactate but the D-lactate isomer can occur in patients with jejunoileal bypass, small bowel resection, or other types of short bowel syndrome. In these patients, ingested starch and glucose bypass the normal metabolism in the small intestine and lead to increased delivery of nutrients to the colon where gram-positive, anaerobic bacteria (e.g., Lactobacilli) ferment glucose to D-lactate. The D-lactate is absorbed via the portal circulation. 

The lower female genital tract generally is colonized by a large munber of aerobic and anaerobic bacteria. Anaerobes may number 10 organisms per milliliter and often include lactobaciUi, eubacte-ria, Clostridia, anaerobic streptococci, and less frequently, Bacteroides frag il is. Aerobic bacteria most often are streptococci and Staphylococcus epidermidis, and these may munber 10 organisms per milbliter. 

The azo link of sulfasalazine is split by anaerobic bacteria in the colon to release sulphapyridine and 5-aminosaiicylic acid, the latter being the active metabolite that acts locally in the treatment of inflammatory bowel disease. Antibacterials that decimate the gut flora can apparently reduce this conversion and this is reflected in lower plasma levels. Rifampicin also possibly increases the metabolism of the sulphapyridine. 

Salyers AA, West SEH, Vercellotti JR, Wilkins TD. Fermentation of mucins and plant polysaccharides by anaerobic bacteria from human colon. Appl Environ Microbiol. 1977 34(5) 529-533. 

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