Intro to-immunity-with-narration


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Intro to-immunity-with-narration

  1. 1. <ul><li>Host-microbe relationships </li></ul><ul><li>Disease processes </li></ul><ul><li>Epidemiology </li></ul><ul><li>Nosocomial infections </li></ul>Introduction to Immunity
  2. 2. Host-Microbe Relationships <ul><li>What do the following terms mean? </li></ul><ul><li>Pathogen </li></ul><ul><li>Host </li></ul><ul><li>Symbiosis </li></ul><ul><ul><li>Symbiosis includes: </li></ul></ul><ul><ul><ul><li>mutualism </li></ul></ul></ul><ul><ul><ul><li>commensalism </li></ul></ul></ul><ul><ul><ul><li>parasitism </li></ul></ul></ul>
  3. 3. Example of Mutualism: Bacteria on The Human Skin
  4. 4. Contamination, Infection, & Disease <ul><li>Contamination : the presence of microbes </li></ul><ul><li>Infection : the multiplication of any parasitic organism in or on a host </li></ul><ul><li>Disease : a change in the state of health in which tissues/organs are disrupted or damaged. </li></ul><ul><li>Can be viewed as a sequence of increasing severity (contamination infection disease) </li></ul>
  5. 5. Pathogenicity vs. Virulence <ul><li>Pathogenicity : the ability of an organism to cause disease </li></ul><ul><li>Virulence : the intensity (or degree) to which an organism causes disease </li></ul>
  6. 6. Microflora (Flora, Microbiota) <ul><li>Organisms that live on or in the body but under normal circumstances do not cause disease </li></ul>Types: Resident microflora (normal flora): comprise microbes that are always present in or on the human body Transient microflora: microbes that can be present under certain conditions in any of the locations where resident microflora are found
  7. 7. Opportunistic Organisms <ul><li>Organisms that do not normally cause disease, but take advantage of particular opportunities to cause disease. </li></ul><ul><li>Immunocompromised individuals commonly become infected with opportunistic organisms </li></ul>
  8. 8. Kinds of Diseases <ul><li>Human diseases are caused by infectious agents, structural or functional genetic defects, environmental factors, or any combination of these causes </li></ul><ul><li>Infectious Diseases: caused by infectious agents such as bacteria, viruses, fungi, protozoa, & helminths </li></ul><ul><li>Noninfectious Diseases: caused by any factor other than infectious organisms </li></ul>
  9. 9. Microbiology focuses on Infectious Diseases <ul><li>Communicable disease : a disease that can be transmitted from one person to another </li></ul><ul><li>What are examples of communicable microbial diseases? </li></ul><ul><li>Noncommunicable disease : a disease that cannot be transmitted from one person to another </li></ul><ul><li>What are examples of noncommunicable microbial diseases? </li></ul>
  10. 10. Types of Infectious Diseases <ul><li>Acute : develops rapidly & runs its course quickly (measles & cold) </li></ul><ul><li>Chronic : develops more slowly than an acute disease, is usually less severe, & persists for a long, indeterminate period (tuberculosis) </li></ul><ul><li>Subacute : intermediate between an acute & a chronic disease (gingivitis) </li></ul><ul><li>Latent : characterized by periods of inactivity either before signs & symptoms appear (herpes virus) </li></ul>
  11. 11. Stages of an Infectious Disease <ul><li>Incubation period: time between infection & appearance of signs and symptoms </li></ul><ul><li>Prodromal phase: a short period of nonspecific, often mild, symptoms (malaise and headache) </li></ul><ul><li>Invasive phase: period when the individual experiences the typical signs & symptoms of the disease </li></ul><ul><li>Acme : period during invasive phase where </li></ul><ul><li>symptoms & signs are most severe </li></ul><ul><li>Decline phase: the period of illness when host defenses & effects of treatment overcome the pathogen </li></ul><ul><li>Convalescent period: tissues are repaired, healing takes place, & body regains strength & recovers </li></ul>
  12. 12. Stages of an Infectious Disease
  13. 13. Signs, Symptoms, & Syndromes <ul><li>Most diseases are recognized by signs & symptoms </li></ul><ul><li>Sign : a characteristic of a disease that can be observed by examining the patient (e.g. swelling, redness, rashes, coughing, pus, runny nose, vomiting) </li></ul><ul><li>Symptom : a characteristic of a disease that can be observed or felt only by the patient (e.g. pain, shortness of breath, nausea, sore throat, headache) </li></ul><ul><li>Syndrome : a combination of signs & symptoms occurring together & are indicative of a particular disease or abnormal condition </li></ul><ul><li>Sequelae : even after recovery, some diseases leave after-effects (e.g. valve damage) </li></ul>
  14. 14. Epidemiology, Incidence & Prevelance <ul><li>Epidemiology : the study of factors & mechanisms involved in the frequency & spread of diseases & health-related problems </li></ul><ul><li>Etiology : the assignment or study of causes and origins of a disease </li></ul><ul><li>Incidence of a disease: the number of new cases contracted within a set population during a specific period of time </li></ul><ul><li>Prevalence of a disease: the total number of people infected within the population at any time </li></ul>
  15. 15. Diseases in Populations <ul><li>Endemic : disease is present continually in the population of a particular geographic area </li></ul><ul><li>Epidemic : a higher-than-normal incidence of a disease in a population </li></ul><ul><li>Pandemic : worldwide disease </li></ul>
  16. 16. The Spread of Cholera <ul><li>Began in Peru in 1991 </li></ul><ul><li>Moved to Columbia & Ecuador </li></ul><ul><li>Late 1992: epidemic spread to Venezuela, Bolivia, Chile, & Brazil in South America </li></ul><ul><li>Then to Guatemala, Honduras, Panama, Nicaragua, & El Salvador in Central America </li></ul>
  17. 17. Reservoirs of Infection <ul><li>Reservoirs: Sites in which organisms can persist & maintain their ability to infect </li></ul><ul><li>Essential for new human infections to occur </li></ul><ul><ul><li>Humans </li></ul></ul><ul><ul><li>Other animals (including insects) </li></ul></ul><ul><ul><li>Plants </li></ul></ul><ul><ul><li>Certain nonliving material (water & soil) </li></ul></ul><ul><li>Zoonoses: diseases that can be transmitted under natural conditions to humans from other vertebrate animals (rabies) </li></ul>
  18. 18. Modes of Disease Transmission- Contact Transmission <ul><li>direct contact </li></ul><ul><li>indirect contact (fomites) </li></ul><ul><li>droplets </li></ul>
  19. 19. Modes of Disease Transmission- Vehicle transmission <ul><ul><li>water </li></ul></ul><ul><ul><li>air </li></ul></ul><ul><ul><li>food </li></ul></ul>
  20. 20. Droplet Transmission
  21. 21. <ul><li>Modes of Disease Transmission- Vector transmission </li></ul><ul><ul><li>mechanical </li></ul></ul><ul><ul><li>biological </li></ul></ul>
  22. 22. Controlling Disease Transmission <ul><li>Isolation : A patient with a communicable disease is prevented from having contact with the general population </li></ul><ul><li>Quarantine : the separation of “healthy” human or animal carriers from the general population when they have been exposed to a communicable disease </li></ul>
  23. 24. Modes of Disease Transmission- Summary <ul><li>Contact Transmission </li></ul><ul><ul><li>Can be direct, indirect, or by droplets </li></ul></ul><ul><ul><li>Direct contact requires body contact between individuals </li></ul></ul><ul><ul><li>Indirect contact occurs through fomites </li></ul></ul><ul><ul><li>Droplet: occurs when a person coughs, sneezes, or speaks near others </li></ul></ul><ul><li>Vehicle Transmission </li></ul><ul><ul><li>Nonliving carrier of an infectious agent from its reservoir to a susceptible host </li></ul></ul><ul><ul><li>Water </li></ul></ul><ul><ul><li>Air </li></ul></ul><ul><ul><li>Food </li></ul></ul><ul><li>Vector-Borne Transmission </li></ul><ul><ul><li>Vectors: Living organisms that transmit disease to humans </li></ul></ul><ul><ul><li>Most vectors are arthropods: ticks, flies, fleas, lice & mosquitoes </li></ul></ul>
  24. 25. How Fungi & Protozoa Cause Disease <ul><li>Fungi </li></ul><ul><li>Spores that are inhaled or enter cells through a cut or wound </li></ul><ul><li>Some fungi produce mycotoxins </li></ul><ul><li>Protozoa </li></ul><ul><li>invade & reproduce in red blood cells </li></ul><ul><li>attach to tissues & digest them </li></ul><ul><li>Produce cysts (dormant forms) as a means of disease transmission & trophozoites (active, multiplying forms) </li></ul>
  25. 26. Factors Affecting Disease Establishment <ul><li>Portal of Entry </li></ul><ul><li>Adhesive Factors </li></ul><ul><li>Dose </li></ul><ul><li>Tissue Penetration </li></ul><ul><li>Enzymes </li></ul><ul><li>Toxins </li></ul><ul><ul><li>Toxins, enzymes, & adhesive factors are sometimes referred to as virulence factors </li></ul></ul>
  26. 27. Portal of Entry <ul><li>Site of entry of microbes </li></ul><ul><ul><li>Includes skin, mucous membranes, openings of the respiratory, digestive, & genitourinary systems, & crossing the placenta </li></ul></ul><ul><li>May involve adhesive factors, also known as adhesins (include certain surface proteins/ glycoproteins, fimbriae, & capsules) </li></ul>
  27. 28. Portals of Exit sites where microbes leave the body
  28. 29. Dose <ul><li>The number of infective particles required to lead to colonization </li></ul><ul><li>Colonization refers to the growth & reproduction of microorganisms on host tissues </li></ul><ul><li>Exposure to a low dose can result in immunity </li></ul>
  29. 30. Tissue Penetration <ul><li>The ability of a microbe to enter host tissue </li></ul><ul><li>Visible in tissue preparation </li></ul><ul><li>Not required for every disease </li></ul><ul><li>The ability of a microbe to invade tissue & damage it is known as its invasiveness </li></ul>
  30. 31. Enzymes <ul><li>Coagulase </li></ul><ul><li>Streptokinase </li></ul><ul><li>Hyaluronidase </li></ul><ul><li>Hemolysins </li></ul><ul><li>Leukocidin </li></ul><ul><li>Collagenase </li></ul>
  31. 32. Coagulase : clots fibrin in blood plasma. Bacteria form a fibrin clot around themselves protecting them the host’s immune system ( S. aureus ) Streptokinase : dissolves fibrin clots ( Streptococcus ) Enzymes
  32. 33. Hyaluronidase: enzyme digests hyaluronic acid Enzymes
  33. 34. Hemolysins: enzymes that breakdown red blood cells (RBCs) 3 Types of hemolysis : 1- Gamma hemolyis : no breakdown of RBCs 2- Alpha (  ): partial breakdown of RBCs; greenish-grey coloration 3- Beta or complete hemolysis (  ): complete breakdown of RBCs; clear zones around colonies Alpha Beta Streptococcus pneumoniae Streptococcus pyogenes Enzymes
  34. 35. Enzymes <ul><li>Collagenase : enzyme that degrades collagen ( Clostridium ) </li></ul><ul><li>Leukocidin : enzyme that degrades white blood cells </li></ul>
  35. 36. Bacterial Toxins <ul><li>A substance that is poisonous to another organism </li></ul><ul><li>Two types: </li></ul><ul><ul><li>Exotoxin : a toxin produced by a cell & is secreted outside the cell to affect host tissue </li></ul></ul><ul><ul><li>Endotoxin : a toxin that is a portion of the cell (usually the cell wall) & is released into host tissues </li></ul></ul><ul><ul><ul><li>Characteristic of Gram negative bacteria </li></ul></ul></ul>
  36. 37. Nosocomial Infections : a n infection acquired in a hospital or other medical facility Where do the bacteria causing nosocomial infections come from? Common Causative Agents of Nosocomial Infections
  37. 38. Some Common Modes of Transmission of Nosocomial Infections
  38. 39. Relative Frequencies of Sites of Nosocomial Infections
  39. 40. <ul><li>Latex gloves </li></ul><ul><li>Eye protection </li></ul><ul><li>Mask </li></ul><ul><li>Sterile Equipment </li></ul>Infection Control