The E Coli Is A Gram Negative, Rod Shaped Bacterium

1035 WordsMar 8, 20155 Pages
The E-coli is a gram-negative, rod-shaped bacterium. It can grow under aerobic (extra-intestinal) or anaerobic conditions (intestine) and is the predominant facultive organism in human’s GI tract. It belongs to the bacterial family of Enterobacteriaceae. It is an important member of the intestinal human’s micro-flora. It usually adheres to the mucus overlying the large intestine. Nowadays, pathogenic E-coli are classified based on their unique virulence factors. Pathogenic strains of the bacterium cause three different diseases: (8) • Urinary tract infections • Neonatal meningitis • Intestinal diseases Each of the diseases depends on different expression of virulence factors such as adhesins, invasins, chemotaxis, toxins and the ability of the E-coli to defend its host. (8) Uropathogenic E-coli colonize from perineal region and ascend to the bladder. The virulence factor expressed is P fimbria. The strains also express other virulence factors such as siderophores that play a role in obtainment of iron for the bacteria. They also express haemolysins. A-haemolysin lyse the lymphocytes and β-haemolysin inhibits the phagocytosis of neutrophils. Another virulence factor is the resistance to the complement-dependent bactericidal effect. The presence of K antigens promotes bacterial virulence by decreasing the ability of antibodies or complement to bind to the bacterial cell surface and cause the loss of phagocyte’s ability to recognize and destroy them. (8) Neonatal meningitis
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