Pathogens of microorganisms on microbiology.pptx

Microorganisms are all around us, and while many are harmless or even beneficial, some can cause disease. These disease-causing microorganisms are called pathogens.

There are five main types of pathogens:

Viruses: These are the smallest and simplest type of pathogen. They are not living organisms and cannot reproduce on their own. Instead, they invade host cells and use the host's machinery to replicate. Viruses can cause a variety of diseases, including the common cold, influenza, HIV/AIDS, and COVID-19.
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Virus pathogen
Bacteria: Bacteria are single-celled organisms that can reproduce on their own. They can cause a variety of diseases, including food poisoning, strep throat, pneumonia, and tuberculosis.
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Bacteria pathogen
Fungi: Fungi are eukaryotic organisms that can be single-celled or multicellular. Some fungi can cause diseases in humans, such as athlete's foot, ringworm, and yeast infections.
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Fungi pathogen
Protozoa: Protozoa are single-celled eukaryotic organisms that can be motile or nonmotile. Some protozoa can cause diseases in humans, such as malaria, giardia, and toxoplasmosis.
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Protozoa pathogen
Helminths: Helminths are parasitic worms that can live in the human body. They can cause a variety of diseases, including trichinosis, pinworm infection, and tapeworm infection.
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Helminths pathogen
Not all microorganisms are pathogens. In fact, many microorganisms are beneficial to humans. For example, the bacteria in our gut help us digest food, and the bacteria in our skin help protect us from harmful pathogens.

The severity of a disease caused by a pathogen depends on a number of factors, including the type of pathogen, the person's immune system, and the person's age and overall health.

1. PATHOGENESIS OF MICROORGANISM 1

2. Microbial Pathogenesis: Microbial pathogenesis is the ability of microbes, or their components, to cause infection in a host after developing a complex mode of interactions from both hosts and pathogens. Pathogens: A pathogen is an infectious agent (“germ”) that causes disease or illness in a host. Infection: An infection is the invasion of an organism's body tissues by disease-causing agents, their multiplication, and the reaction of host tissues to the infectious agents and the toxins they produce. 2

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4. How Microorganism Enter A Host Portals Of Entry Mucus Membranes Skin The Parenteral Route The Preferred Portal of Entry Numbers of Invading Microbes Adherence 4

5. Mucus membranes: The most common route for most pathogens. Entry through mucus membranes of: 1. respiratory tract (most common) 2. gastrointestinal tract 3. urinary/genital tracts 4. conjunctive Skin: 1.Some pathogens infect hair follicles and sweat glands 2.Few can colonize surface. Portals of Entry: 5

6. Portals of Entry for the Pathogens of Some Common Diseases: 6

7. Numbers of Invading Microbes: Likelihood of disease increases as the number of invading pathogens increases. Adherence: Adherence attachment to the host by the microbe at portalof entry. Blocking adhesion can prevent diseasepathogen has surface molecules called adhesions orligands that bind specifically to the host surface receptors. Most microbial adhesions are glycoproteins or lipoproteins located on the glycocalyx, capsule, capsid, pili, fimbriae orHost cellsurfaceflagella . Most host receptors are typically proteins (for virus) or carbohydrates (for bacteria) in the wall or membrane of host cell. 7

8. Adherence: 8

9. How Bacterial Pathogens Penetrate Host Defenses Capsules Components of cell wall Enzymes Antigenic variation Penetration into host cell cytoskeleton. 9

10. Capsules: Capsules-organized glycocalyx layer (carbohydrates) outside cell wall. Impairs phagocytosis: prevents engulfment and destruction byleukocytes . If present, is usually required for virulence. Components of Cell Wall: M protein of Streptococcus pyogenes: Heat and acid resistant Mediates attachment of bacterium to epithelial cells resists. phagocytosis by leukocytes. 10

11. Fimbriae + Opa (membrane protein): Used by Neisseria gonorrhoeae: -promote attachment and uptake by host epithelial cells and leukocytes. Neisseria then grows inside these cells. Mycolic acid (waxy) of Mycobacterium tuberculosis: Resist digestion by phagocytes -Mycobacterium then grows inside phagocyte. 11

12. Enzymes: Also known as Exoenzymes. Coagulases: Clot fibrin in blood to create protective barrier against host defenses . Kinases: Dissolve clots (fibrinolysis) to allow escape fromisolated woundse.g . Streptokinase (Streptococcus pyogenes) Staphylokinase (Staphylococcus aureus). Hyaluronidase: Hydrolyzes hyaluronic acid ("glue' that holds together connective tissues and epithelium barriers) allowing deeper invasion. e.g. Clostridium species:allows them to cause gangrene (tissue necrosis). 12

13. Collagenase: Breaks down collagen (fibrous part of connective tissue) for invasion into muscles and organs e.g. Clostridium species. IgA proteases: Destroy host IgA antibodies found in mucous secretions to allow adherence and passage at mucus membranes e.g. Neisseria species that infect CNS. Antigenic Variation: Pathogen alters its surface antigens to escape attack by antibodies andimmune cells. e.g. Neisseria gonorrhoeae has many versions of the Opa gene, it canalter which one is being expressed. 13

14. How Bacterial Pathogens Damage Host Cells 14 If pathogen overcome host defense then microorganism can damage host cells by: Using host cells nutrients. Causing direct damage. Inducing hypersensitivity reactions Producing toxins  .

15. Using hosts nutrients: (e.g. iron) Required for all cells (electron transport chain: cytochromes) both host and pathogen. Host usually does not have free iron available (free iron leads to easy colonizationby pathogens). Humans bind unused iron to transport proteins: transferrin. Pathogens can produce siderophores (iron carrier): secreted by bacteria to competeiron from host proteins, siderophore iron complex then absorbed by bacteria. 15

16. Direct damage to colonized area: Growth and replication in host cells: results in host cell lysis. Penetration through host cells (mucosa, organs) causes damage. Lysis of host cells to obtain nutrients. Producing toxin: Toxins are of two genereal types , based on their position relative to the microbial cell: Exotoxins & Endotoxins . 16

17. Exotoxins: Produced inside the bacteria and either secreted or released following microbelysis . Function to destroy certain host cell parts or inhibit particular metabolic functions . Damage from toxin results in the particular signs or symptoms of a disease. Can be named for the disease, type of cell attacked or organism that produces it e.g. tetanus toxin: causes tetanus (contraction) of muscle. 17

18. Endotoxins: Part of the outer membrane portion of the cell wall of gram negative bacteria: Lipopolysaccharide (LPS) Released when dead cells lyse In blood, causes macrophages to release high levels of cytokines resulting in chills, fever, weakness, aches, small blood clots, tissue necrosis, shock and death. Sterile solutions can contain LPS: bacteria dies in sterilization but LPS is unaltered. Due to serious consequences at very low levels of LPS, it is essential totest medical devices and solutions for endotoxin. 18

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21. Pathogenic Properties & Stages of Viruses 21 Viral pathogenesis comprises of several stages including- (1) transmission and entry of the virus into the host. (2) spread in the host. (3) tropism. (4) virulence and cytopathogenicity. (5) patterns of viral infection and disease. (6) host factors. (7) host defense. (8) virus-induced immunopathology.

22. Pathogenic Properties of Fungi, Protozoa, Helminths, Algae. Fungi: ( 1)Fungal waste products may cause symptoms. (2)Chronic infections provoke alargic  response  . Protozoa: (1) Amoebic dysentery. (2) Balantidiasis. (3)malaria, cryptosporidium. 22

23. Helmenthis : (1)Use host tissue. (2) Presence of parasite interferes with host function. (3) Parasite metabolic waste can causes symptoms. Algae: (1) Neurotoxins produced by dinoflagellates- SaxitoxinParalytic shellfish poisoning. 23

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26. Immunopathogenesis In certain diseases, the symptoms are caused not by the organism itself, but due to immune response to the presence of organisms. For example, immune complexes deposited in the glomerulus of the kidney cause poststreptococcal glo- merulo nephritis. Antibodies that are produced against the M proteins of S. pyogenes cross-react with joint, heart, and brain tissues producing disease manifestations of rheumatic fever. Similarly, the host immune response is an important cause of disease symptoms in patients suffering from syphilis caused by T. pallidum, Lyme disease caused by Borrelia, and other diseases. 26

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29. Made By Md Tofayel Mojumder Depertment of Pharmacy ,Northern University Bangladesh 29