Bacterial Toxins

Bacterial toxins are proteins that exist on the cell membrane and make bacteria more pyrogenic and resistant.

Gram positive bacteria have peptidoglycans, teichoic acid and lipotechoic acid in their cell wall, which act as adhesions and regulate cell wall synthesis.

Gram negative Bacteria have a Lipopolysaccharide layer. Lipid A is responsible for toxicity and pyrogenicity (Ngqwala, 2017). Bacteria can survive in harsh conditions by producing spores and can form resistance to treatment of diseases.

Exotoxins are proteins secreted by Gram positive and gram negative bacteria and are highly toxic. Endotoxins are lipopolysaccharides, weakly toxic and not fatal. Enterotoxins are a type of Exotoxins and cause chemical imbalances (N. Gilani, 2017).

4.1

Enterotoxins

Enterotoxins are protein exotoxins, secreted by bacteria, toxic, heat-stable, water soluble, have low molecular weight and form pores in cell membranes.

They target intestines and the digestive system and alter the permeability of the membrane of mucosal-epithelial cells of the walls.

4.2

Clinical significance of Enterotoxins

Enterotoxins increases chloride ion permeability of the intestinal mucosal cell’s apical membrane leading to leakage into the lumen and sodium and water movement. The membrane’s pores are activated by increased Camp or intracellular calcium-ion concentration.

4.3

Staphylococcal Enterotoxins

 Staphylococcal enterotoxins bind to the major histocompatibility complex (proteins needed for the immune system to recognize foreign molecules) in their hosts.

Staphylococcal food poisoning(SFP) is an illness resulting from consuming foods containing large amounts of enterotoxins.

4.3

Exotoxins

Exotoxins are proteins released by Gram-positive and Gram-negative bacteria.

The genes of exotoxins are found either in the plasmid or bacteriophage.

Exotoxins are toxic, not heat-resistant and can be destroyed at low temperatures (team, 2017).

Exotoxins are divided into three different categories, namely; A-B toxins such as Corynebacterium diphtheria, the diphtheria toxin, which blocks protein synthesis; membrane disrupting toxins such as

Staphylococcus aureus, which digest cell membranes and lastly, superantigens such as Staphylococcus aureus, where the immune system cells ‘accidentally’ damage the body and this results in toxic shock syndrome. (Rao) (Shmaefsky, 2009)

4.4

Endotoxins

Another class of bacterial toxins is endotoxins. Endotoxins are agents of pyrogenicity of some gram negative bacteria such as the Brucella species. The lipopolysaccharides in bacterial cell walls are the endotoxin, and this is only released once lysis of the bacterial cell occurs. They are less potent than exotoxins and in large quantities; they produce toxic shock and severe diarrhoea. (Galanos & Freudenburg)

4.5

Endotoxin Shock

Endotoxin shock occurs when endotoxins stimulate the release of inflammatory cytokines among other things, resulting in smooth muscle relaxation, vasodilation and increased vascular permeability. Patients often present with fever and hypotension. (Endotoxic Shock)Diseases

4.6

Endotoxin sources

There are many sources of endotoxins, for example in parenteral and medical device products and the main source is water. In this case removal is essential, and this can be done based on the following processes; adsorption, two-phase partitioning, ultrafiltration and chromatography. Failure to remove can result in pyrogenic responses. (Bacterial Endotoxins/Pyrogens, 1985).

4.7

Fortunately the effects of exposure to endotoxins can be treated. Early empiric broad spectrum antibiotic therapy in patients showing symptoms of toxic shock has been shown to improve survival (Endotoxic Shock)

4.8

 

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