Gram-negative bacteria endotoxins

Endotoxins are the lipopolysaccharides (LPS) of the outer membrane of Gram-negative bacteria. They trigger inflammatory reactions in the infected organism, activate complement and cause fever or even a septic shock. They act on toll-like receptors. 

A lipopolysaccharide (LPS) is any compound consisting of covalently linked lipids and polysaccharides. The term is used more frequently to denote a cell wall component from Gram-negative bacteria. LPS has endotoxin activities and is a polyclonal stimulator of B-lymphocytes. 

Fever is the most common manifestation. The thermoregulatory centre in the hypothalamus regulates body temperature and this can be affected by endotoxins (heat-stable lipopolysaccharides) of Gram-negative bacteria and also by a monokine secreted by monocytes and macrophages called interleukin-1 (IL-1) which is also termed endogenous pyrogen. Antibody production and T-cell proliferation have been shown to be enhanced at elevated body temperatures and thus are beneficial effects of fever. 

Ulevitch, R.J. and Tobias, P.S. (1999) Recognition of gram-negative bacteria and endotoxin by the innate immune system. Current Opinion in Immunology 11, 19-22. 

Despite rigorous implementation of GMP, most biopharmaceutical preparations will be contaminated with low levels of Gram-negative bacteria at some stage of manufacture. These bacteria shed endotoxin into the product stream, which is not removed during subsequent bacterial filtration steps. This is one of many reasons why GMP dictates that the level of bioburden in the product stream should be minimized at all stages of manufacture. 

Arnold and Brown (1978) reported on the possibility that bacterial endotoxins, which are widespread, could result in hypersensitivity to histamine. These compounds are complex, heat-stable, lipopolysaccharide materials produced primarily by Gram-negative bacteria. They also reported that endotoxin is known to be capable of inducing histamine release in animals (sometimes called endotoxin shock) similar to that seen in anaphylaxis. Baranowski et al. (1990), however, reported extremely low levels of endotoxin in both good tuna and tuna known to have caused illness in humans. 

There is no strong correlation between byssinosis and levels of viable bacteria in a given plant. Symptoms are, however, more compatible with those produced by endotoxins. Endotoxins are pathogenic agents produced by gram-negative bacteria and are primarily llpopolysaccharide (IPS) in nature. 

Endotoxin. Endotoxin is the lipopolysaccharide that comprises a major portion of the cell wall of the gram-negative bacteria. The endotoxins from each species of bacteria are different but the lipid A moiety is similar for the Enterobacterlaceae, and has a similar series of biological actions regardless of its source. The lipid A material is different in some of the gram-negative rods present in cotton (i.e. in the Pseudomonas species). This variety of compounds makes quantitation of endotoxin difficult. Hence, it is usually measured by its biological activity as compared to a standard endotoxin (usually that of E. coll). (See Table VIII.)... 

The determination of the endotoxin with limulus amebocyte lysate (LAL) is based on gel formation of a mixture consisting of a solution of endotoxin of Gram-negative bacteria with a solution of lysate. The extent and speed of the reaction depend on the endotoxin concentration, pLL, and temperature. The reaction requires the presence of certain cations, a proclotting enzymes system, and clottable protein, which are produced by lysate. 

The polymyxins are a group of basic peptides active against gram-negative bacteria and include polymyxin and polymyxin E (colistin). Polymyxins act like cationic detergents. They attach to and disrupt bacterial cell membranes. They also bind and inactivate endotoxin. Gram-positive organisms, proteus, and neisseria are resistant. 

The 3-deoxy-D-ma/ino-2-octulosonic acid 8-phosphate synthase (KDO synthase or KdoS EC 4.1.2.16) is an enzyme involved in the biosynthesis of the eight-carbon sugar KDO [63], a constituent of the capsular polysaccharides (K-antigens) and outer membrane lipopolysaccharides (LPS, endotoxin) of Gram-negative bacteria [156], as well as of the cell wall of algae and a variety of plants [157], In vivo, the enzyme catalyzes the irreversible addition of 26 to D-arabinose 5-phosphate (Ara5P, 32) to form KDO 8-phosphate 33 [158]. The... 

We found that P3 combined with cell walls of endotoxin containing gram-negative bacteria, such as Escherichia coli and Salmonella, induced complete regression of line 10 tumors (6 ). 

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