L2 - Host-Parasite relationship.pdf

L2 - Host-Parasite relationship File Edit Index: Main Text Girls Slides Important Doctors Notes Boys Slides Extra Info  Objectives Define core...

L2 - Host-Parasite relationship File Edit Index: Main Text Girls Slides Important Doctors Notes Boys Slides Extra Info  Objectives Define core terms related to Recall the transmissibility of 01 host-parasite relationship. 05 pathogenicity Recall host response to parasite invasion Describe the attributes of 02 (specific and non-specific responses). 06 pathogenicity and recall examples. Know important examples of primary Know the infection chain and 03 and secondary pathogens. 07 infectious disease process Recognize the differences between 04 virulence and pathogenicity and how 08 Know Koch’s Postulates virulence is measured Host-Parasite Relationship : Host: human, animal or, parasite: A bacteria, other organisms that support viruses, fungi or parasites which the growth and survival and live in or within the host, may protection of the parasite cause disease or live mutually with the host. - Human host is normally in contact with many microorganisms (microbiota/normal flora) The word parasite in the title which are all bacteria and organisms in our body that cause no harm and disease and may be beneficial “Host-Parasite Relationship” means any living microorganism. - Only a small number of these microorganism (primary and opportunistic pathogens) can cause disease. - Host-parasite relationships (interaction) is characterized by fighting the organism trying to invade the body and the body defending itself by protective measures. All defense lines in our body ex: WBC, tonsils, Stomach PH.... - Host-parasite relationship is discussed under : pathogenicity & microbiota  Not every person that is infected Definitions : has an infectious disease, but every person that has an infectious disease is infected. Pathogenicity: Infection: invasion of Infectious disease: is the end the ability of the cells and multiplication by product of an infectious process with microorganism to cause microorganisms without tissue tissue destruction depends on both host diseases destruction. Shows no symptoms immunity and pathogen virulence. Shows signs and symptoms of infection Resistance: The Susceptibility: Lack of Transmissibility: The ability to spread from one host to ability of the host to prevent resistance to an organism and another. This enables the establishment of infection by establishment of disease. ‫ﻟﻠﻌدوى ﻋرﺿﺔ‬ microorganism to maintain continuity using its defense mechanisms. of its species in the event of death of original host. Modes of transmission: 1. Airborne (cough) 2. contact(water, food) 3. vehicle or vector(flies) Pathogen : Pathogen (infectious agent): is a microorganism having the capacity to cause a disease in a particular host. - A pathogen may infect one body organ or multiple organs. - Some pathogens enter into latent state (infection but no symptoms) - Eg. Mycobacterium tuberculosis (bacteria that cause TB), Herpes virus Not part of the normal flora. Opportunistic (secondary) Primary (true) pathogens Pathogen pathogens (part-time bad guys) (full-time bad guys) (divided according to the degree of pathogenicity) An organism that is able to cause disease in Having low pathogenicity and infects people an apparently healthy individual who is with low immunity. non-immune to that organism. -Causes disease in immunocompromised host -Causes disease in healthy individuals -Gain access (injures) to sterile regions. -Associated with a specific & recognizable disease Example: 1-Pseudomona Example: 2-S. epidermidis (staphylococcus 1-Bordetella species epidermidis) 2-Mycobacterium Tuberculosis  Virulence : Virulence is the degree of pathogenicity ( severity / harmfulness), or the ability to invade and destroy tissue to produce disease. by toxins, certain enzymes, or their capsid Virulence is measured by : the Lethal dose 50 (LD50) which is the number or amount of organisms or mg of toxins that will kill 50% of susceptible lab animals ( usually mice ) when injected into such animals. - When the LD50 is small, the microorganism is considered highly virulent. - When the LD50 is high the microorganism is considered having low virulence. (‫)ﻋﻼﻗﺔ ﻋﻛﺳﯾﺔ‬ Eg. Shigella species is more virulent than Salmonella species. Note: Virulence factors for the bacteria are the capsule, endotoxins and exotoxins. - Virulence is predominantly associated with adherence and colonization, invasion, avoidance of host responses and toxin formation. Host Resistance To Parasite Invasion: Non specific defense is part of Specific defense is an acquired natural constitution of the host: resistance to certain organism: Skin mechanical barrier (burn patients can Formation of Antibodies (after getting a suffer from serious infections due to lack to this barrier) virus your body forms antibodies to the virus) Ciliated epithelium of respiratory tract (make you cough) Competition by normal flora (AKA microbiota) Low pH of the stomach (vagina has low pH=4) Cough Peristalsis (the movement of intestines or esophagus) Lysozymes (Eg. in tears) (destroying peptidoglycan , thus killing the bacteria) Neutrophils (white blood cell) Determinants of Pathogenicity: Before causing disease, the microorganism should have the ability to: Adherence and Survive (resist): Multiply: Tissue colonization: Destruction: Attachment to host Resist host natural Multiply to large the ability to overcome epithelial surface. defense numbers. host defense, invade the tissues and cause Adhesins: factors that mechanisms. helps to cause adherence destruction to produce Eg. pili. clinical disease. By toxins formation Adherence and Colonization: adhesins : adherence factors found on bacterial surfaces. Factors of Adhesion Found on bacterial Structures found on surfaces host cells 1. Pili 2. Other protein surface 1. Fibronectin structures 2. Proteins and 3. Capsid spikes of Glycopeptide viruses Adherence and Colonization: Tissue Destruction: Tissue Destruction Toxin Production Invasion Exotoxin Non-Capsulated Capsulated Endotoxin Organism Organism Produced outside gram Only in gram (+ve) & (-ve) bacteria. (-ve) bacteria. Bacteria without Bacteria that have Example: Cholera Toxin Part of the outer capsule. capsule. They resist intracellular killing, membrane. being called intracellular (IC) Examples: S. pneumoniae More dangerous (Pneumococcus) organisms. Examples: Mycobacterium tuberculosis, Haemophilus influenzae Salmonella typhi, Brucella species, etc. Exotoxin Types: Example: Haemolysin of Example: Exotoxin group A Cholera Toxin Streptococci A-B Type Membrane Exotoxins Active Exotoxin Enters cell via: A: Active unit B: Binding 1- Receptor mediated endocytosis. 2- Fusion of vesicle with lysosome. unit for 3- Acid environment of the lysosome reduces disulfide bonds and Enters the ribosome attachment releases into the cell. and stops protein synthesis. Helps bacteria attach to cell membrane. Exotoxin Vs. Endotoxin High Immunogenicity (Capable of Inactivated Pharmacologically provoking the by immune system, No specific action chemicals Exotoxin Soluble & Heat Labile (Goes to a specific and trigger or Protein (Destroyed by site and causes a induce the to form (More specific) diffusible heat/changing) specific action) production of neutralizing toxoids fever antibodies, which (Such as will target the effect of toxins) vaccines) Part of the cell wall Non Specific Low (out of membrane in Gram(-ve)) Stays (Which is considered more Immunogenicity (Not capable of Does dangerous since provoking the Heat not within bacterium Endotoxin Lipopolysaccharide cell, until the bacteria is the immune immune system, Induces system becomes thus it cannot Stable form fever (Lipid+Sugar) (Less specific) destroyed, then it confused, thus it produce will be diffused to destroys cells all neutralizing More dangerous toxoids the blood over the body) antibodies) Capsulated Vs. Non-Capsulated Resist intracellular Non-Capsulated Organism Capsulated Organism Resist phagocytosis killing -Resist intracellular killing so it is -They have capsules which protect them, thus they are highly virulent. called intracellular organisms (IC) It lies within the cell because it does not -Bacteria capsules are made of have a capsule that will protect it from polysaccharides, except the capsule of bacillus phagocytosis. anthracis (polypeptide protein) (Bacillus anthracis causes anthrax and was used as a bioweapon) Eg: ➔ The organism is readily killed once phagocytosed Salmonella non-typhi ➔ Capsules prevents the phagocytosis Legionella Pneumophila and capture of the bacteria by the host Mycobacterium Tuberculosis immune system ➔ It is called extracellular organisms (EC) -Primary Pathogen ➔ Lives outside of the cell Salmonella Typhi Important examples: Brucella species S.Pneumoniae(Pneumococcus) Haemophilus Influenzae Chain of infection: Boy’s slides 1. Pathogen source/reservoir (animate or inanimate) 2. Transmission modes (airborne,contact, vehicle, vector) 3. Host susceptibility (immune status,host nutrition, virulence of pathogens, genetic predisposition, etc,) 4. Exiting the host (excretion in faeces, urine, droplets, blood, saliva, or shed from the body). Chain of infection: Boy’s slides Overcome normal defenses, invasive devices, Causative Microorganism capable of causing immunocompromised agent disease. host. Susceptible host Reservoir Respiratory tract, GI tract, broken skin, Chain of infection Environment, Portal humans, animals. Genitourinary tract. Portal of of entry exit Direct contact, Mode of Excretions, transmission indirect contact (eg. secretions, skin, hands, droplets, food). droplets. Infectious Diseases Process: Boy’s slides 01 03 Incubation period Illness Severe disease, From entry, until signs immune system and symptoms start to 02 04 triggered. show. Prodromal Convalescent stage period Clinical signs are Recovery. not sufficient. This stage is before the real symptoms, only non-specific symptoms like lethargy are present. Koch’s Postulates: Pathogen must be found in a subject suffering from the disease, but should never be 01 found in a healthy subject. The organism must be found in all cases of the disease, and it’s distribution in the body should correspond to that of the legions observed in the host. Robert Hermann Koch Pathogen can be isolated from a sick person and grown in a lab. The organism should be (1843-1910) 02 cultured in pure culture demo in all cases of the disease. N.B. Some organisms are yet to be cultured in the lab. eg: Treponema pallidum, M. leprae. Pathogen injected into a healthy person should cause an infection with the same disease (Have the ability to reproduce the disease in other hosts). The organisms should 03 reproduce the disease in other susceptible animal hosts. Injected pathogen can be isolated from newly infected individual and out must be identical to the original pathogen. (Reisolated yet identical). The organism should be 04 cultured, and antibodies to the disease usually develop in the course of the disease.  MCQs Q1. Lack of resistance to an organism and establishment of disease is : A) Infection B) pathogenicity C) Resistance D) Susceptibility Q2. An example for an opportunistic pathogen : A) Staphylococcu B) Mycobacterium C) brodetella D) B & C s epidermidis tuberculosis species Q3. The LD50 for Shigella species is small, therefore, it has… A) High virulence B) Low virulence C) Medium D) No Virulence virulence  MCQs Q4. Exotoxin is secreted outside of : A) Gram (-ve) B) Gram (+ve) C) Gram (-ve) & D) None of the bacteria bacteria (+ve) bacteria above Q5. Bacteria capsules are made of polysaccharides, except the capsule of : A) Staphylococcu B) Mycobacterium C) S. Pneumoniae D) Bacillus s eoidermis tuberculosis anthracis Q6. A non-capsulated organism resists phagocytosis. A) True B) False 1-D 2-A 3-A 4-C 5-D 6-B  Our Team Leaders Members Osama Sarah Basma TBD Aban Alahmari Alshwirkh albahkly Alanazi Yousef TBD Lamar Reema Alzahrani Alkharraz Alniwaisry Omar Fayan Layan TBD Norah Alharbi Alqahtani alotaibi Alrashid Ghazi TBD Jawaher Deemah Almodarra alarfaj alotabi Nada Haya TBD TBD Nada alMuhawwis Alhazani Alzahrani TBD TBD Ghada Alsagar Wareef Albalawi