Microbial Toxins PDF

Applied microbiology “ Microbial toxins “ By Dr. Rasha M. El-Meihy Professor of Agricultural microbiology Microbial toxins Low molecular weight secondary metabolites produced by microorganisms that can be harmful to host living orga...

Applied microbiology “ Microbial toxins “ By Dr. Rasha M. El-Meihy Professor of Agricultural microbiology Microbial toxins Low molecular weight secondary metabolites produced by microorganisms that can be harmful to host living organisms. Microbial-producing microorganisms ❑ Bacteria Bacterial toxins ❑ Fungi Mycotoxins ❑ Alage Phycotoxins  Bacterial Toxins Definition Bacterial toxins are natural compounds produced by bacteria that harmful to host tissues. Classification ❑ Based on site of secretion: Exotoxins - Endotoxins. ❑ Based on the location of body it affects: Enterotoxin – Neurotoxin – Cytotoxin - Hemolysin. Exotoxins are soluble proteins that secreted by bacterial cell extracellularly into the surrounding environment. Gram-positive bacteria create most exotoxins; however, a few Gram-negative bacteria are also involved. Properties Exotoxins are: made up of polypeptides. denatured at temperatures over 60℃ and by UV radiation. one of the most powerful poisons. highly specialized toxins. highly antigenicity (it can boost antibody formation and immunity). Exotoxins are generally more potent and can be classified based on their target sites and mechanisms of action to: Neurotoxins Enterotoxins Exotoxins Cytotoxins Hemolysins  Neurotoxins Enterotoxins Toxins that affect the nervous system. Toxin that affect the gastrointestinal tract, Examples: leading to gastrointestinal symptoms. Botulinum Toxin: Examples: Produced by Clostridium botulinum, it Cholera Toxin: inhibits neurotransmitter release, Produced by Vibrio cholerae, it activates leading to paralysis. adenylate cyclase, causing severe Tetanus Toxin: diarrhea due to electrolyte imbalance. Produced by Clostridium tetani, it Staphylococcal Toxin: interferes with nerve signal Produced by Staphylococcus aureus, transmission, causing muscle stiffness they cause food poisoning. and spasms.  Cytotoxins Hemolysins Toxins that cause direct damage to host Toxins that lyse red blood cells and other cells. cell types. Examples: Examples: Diphtheria Toxin: Alpha-Hemolysin: Produced by Corynebacterium Produced by Staphylococcus aureus, diphtheriae, it inhibits protein it creates pores in the membranes of synthesis in cells. host cells. Shiga Toxin: Streptolysins: Produced by Shigella dysenteriae and Produced by Streptococcus pyogenes, some strains of Escherichia coli, it they damage red and white blood inhibits protein synthesis and cells. damages epithelial cells. Endotoxins Components of the outer membrane of Gram-negative bacteria, typically it is not released until cell lysis. Properties ❑Lipopolysaccharides (LPS) in nature. ❑Found in the outer membrane of Gram-negative bacteria. ❑Stable in heat.  Endotoxins Lipopolysaccharides (LPS) Structure: Composed of a lipid component (lipid A), a core of sugars, and an O- antigen. Mechanism: Trigger host immune responses, which can lead to fever, inflammation, septic shock, and finally potential organs failure. Differences between exotoxins and endotoxin Feature Endotoxins Exotoxins It is a bacterial toxin and a It is a soluble protein that is secreted to the Definition lipopolysaccharide. outside of the bacterial cell. Type of Molecule Lipopolysaccharide Protein Produced By Gram-negative bacteria Both Gram-negative and positive bacteria. Enzymatic activity Does not act as enzymes. Act as enzymes. Toxicity Less Toxic Highly Toxic. Mode of conversion Cannot be converted to toxoid. Can be converted to toxoid. Fatal It doesn’t prove to be fatal. It is often fatal in larger quantities. Within the outer membrane of the Location In the extracellular fluid. bacterium. Antigenicity Less antigenic Highly antigenic Salmonella Typhi (Typhoid), Clostridium tetani (Tetanus), Producers Vibrio cholerae (Cholera). Clostridium botulinum (Botox).  Mycotoxins Definition Mycotoxins are secondary metabolites produced by specific fungi, primarily belonging to the genera Aspergillus, Penicillium, and Fusarium. Sources Mycotoxins can be found in a wide range of agricultural products, including grains, nuts, seeds, dried fruits, and other food items.  Deoxynivalenol Trichothecenes Ochratoxin A Types of mycotoxins Zearalenone Fumonisins Aflatoxins  Aflatoxins Family of toxins produced by certain fungi, primarily Aspergillus flavus. Commonly Found In: Corn, peanuts, and nuts. Health Effects: Carcinogenic (especially linked to liver cancer). Acute toxicity (aflatoxicosis), which leads to liver damage. Aflatoxins reach the human body in two ways: Direct way. Indirect way. There are more than 20 known aflatoxins, but the four main ones are: ❑ Aflatoxin B1 (AFB1) ❑ Aflatoxin B2 (AFB2) ❑ Aflatoxin G1 (AFG1) ❑ Aflatoxin G2 (AFG2) Which can poison the body through the respiratory tract, mucous membranes or skin, leading to hyperactivity of the inflammatory response.  Phycotoxins Definition Phycotoxins are natural toxins produced by various species of algae, particularly those belonging to the classes Dinoflagellates and Diatoms. Sources These toxins can be found in seafood, especially shellfish, as they can accumulate in their tissues through the food chain. Mechanism Phycotoxins can interfere with nerve function, of Toxicity disrupt cellular processes, and cause inflammatory responses. Many phycotoxins, such as saxitoxin, act as potent sodium channel blockers, affecting nerve transmission and leading to paralysis. Health Symptoms of poisoning can vary widely based on Effects the type of toxin and level of exposure, ranging from gastrointestinal disturbances to severe neurological effects and even death.