ISSUE FOCUS FEED & ADDITIVE MAGAZINE August 2022 37 A CONSTANT ANTAGONIST: CONSEQUENCES OF ENDOTOXINS IN ANIMALS All animal species are affected by gram-negative bacteria. Under normal circumstances, the bacteria are present in the gastrointestinal tract in equilibrium with other microorganisms. However, in situations of bacterial challenge—induced by stress, immunosuppression, etc.—the equilibrium can alter and cause an excess of gram-negative bacteria. During these imbalances, endotoxins are produced and released in the animal. It is under circumstances of a high gram-negative to gram-positive bacteria ratio that endotoxins, also known as lipopolysaccharides (LPS), can become a problem. An excess of LPS happens when there is a high turnover of gram-negative bacteria or a rapid destruction of gram-negative bacteria due to the use of antibiotics. An inflammatory pyrogen, lipopolysaccharides can trigger detrimental effects by stimulating an inflammatory reaction in the gastrointestinal tract, and once absorbed, at other sites in the animal. OVERVIEW OF THE ENDOTOXIN’S STRUCTURE What makes gram-negative bacteria differ from gram-positive bacteria is the structure of the cell envelope. Gram-positive bacteria have a cytoplasmic and a peptidoglycan outer membrane. In addition to these layers, gram-negative bacteria have an outer layer. The outer layer contains phospholipids, proteins, and LPS. This LPS consists of three elements: Lipid A (a hydrophobic component that is toxigenic), a core (an oligosaccharide), and O-antigen (hydrophilic component projecting into the extracellular space) (Figure 1). Josep Garcia-Sirera Toxin Binders Product Manager Agrimprove Structure of an endotoxin Figure 1: Typical endotoxin structure. Lipid A is embedded in the outer membrane of gram-negative bacteria
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