Colon Enterobacteriaceae

Bacteria Mainly Gram-positive bacteria Enterobacteriacea In severe forms strict anaerobic species of colonic type... 

Creation of a suitable environment for the growth of colonic microorganisms, such as Bacteroids, Eubacterium, and Enterobacteriaceae, among others ... 

The colon serves four major functions. They are 1) creation of a suitable environment for the growth of colonic microorganisms such as Bacteroids, Eubac-terium, and Enterobacteriaceae 2) storage reservoir of fecal contents 3) expulsion of the contents of the colon at a suitable time and 4) absorption of water and Na from the lumen, concentrating the fecal content, and secretion of K+ and HCOs . The active secretion of K+ is stimulated by mineralocorticoids. 

V. cholerae is a gram-negative baciUus sharing similar characteristics with the family Enterobacteriaceae. Most pathology of cholera results from an enterotoxin (cholera toxin) produced by the bacteria. Conditions that reduce gastric acidity, such as the use of antacids, histamine-receptor blockers, or proton pump inhibitors or infections with Helicobacter pylori, increase the risk for clinical disease. Cholera toxin stimulates adenylate cyclase, which increases intracellular cAMP and results in inhibition of sodium and chloride absorption by microvillli and promotes the secretion of chloride and water by crypt cells. The toxin likely acts along the entire intestinal tract, but most fluid loss occurs in the duodenum. The net effect of the cholera toxin is isotonic fluid secretion (primarily in the small intestine) that exceeds the absorptive capacity of the intestinal tract (primarily the colon). This results in the production of watery diarrhea with electrolyte concentrations similar to that of plasma. 

Adlerberth, I., Carlsson, B., Deman, P., Jalil, F., Khan, S.R., Laisson, P., Mellander, L., Svanborg, C., Wold, A.E., and Hanson, L.A. 1991. Intestinal Colonization with Enterobacteriaceae in Pakistani and Swedish Hospital-Delivered Infants. Acta Paediatrica Scandinavica 80(6-7), 602-610. 

Microbial numbers and species diversity increases in the distal small intestine, with facultative anaerobes as well as more strict anaerobic species such as bacteroides, clostridia. Gram positive cocci and bifidobacteria reaching population levels of up to 10 colony forming units (CFU)/mL contents. The colon is the main site of microbial colonization in the gut, and the microflora is dominated by the strict anaerobes. This microflora is made up of Bacteroides spp., Eubacterium spp., Clostridium spp., Eusobacterium spp, Peptostreptococcus spp., and Bifidobacterium spp., with lower population levels of anaerobic streptococci, lactobacilli, methanogens and sulphate-reducing bacteria (Figure 6.2). Climax microbial populations occur (up to 10 cells/g) and estimates of diversity range from 400 to 500 different bacterial species. The facultative anaerobes such as lactobacilli, streptococci/enterococci and the Enterobacteriaceae occur in population levels about 100-1000-fold lower than strict anaerobes (Moore and Holdeman 1975 Conway 1995). 

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