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Chapter 14 Mechanisms of Infectious  Disease

Chapter 14 Mechanisms of Infectious  Disease

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Chapter 14 Mechanisms of Infectious  Disease

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  1. Essentials of Pathophysiology Chapter 14Mechanisms of Infectious Disease

  2. Creutzfeldt-Jakob disease and mad cow disease are examples of prion-associated diseases. Viruses are capable of replication outside of a living cell. The term portal of entry refers to the process by which a pathogen enters the body. Some fungi are members of normal human microflora. All organisms cause infectious illness in humans. PRE LECTURE QUIZ (TRUE/FALSE) T F T F F

  3. Infections that develop in patients while they are hospitalized are called _________________. Adding the suffix ______________ to the name of the involved tissue usually designates inflammation of an anatomic location. The _________________ stage in the disease course is the period during which the host experiences the maximum impact of the infectious process. ____________________ refers to the collection of signs and symptoms expressed by the host during the disease course Ticks, mosquitos, mites, and lice are examples of ___________________, a type of organism that derives benefits from its biologic relationship with another organism. PRE LECTURE QUIZ Acute –itis Nosocomial Parasites Symptomatology

  4. “Infection” or “colonization” means that microorganisms are multiplying in or on the host Discussion: • Do you have any infections or colonizations at this moment? List as many as you can identify • Are they normal, or are they making you ill? Infection or Colonization with Microorganisms

  5. Over 300 different species of bacteria live in the large intestine Bacteria and fungi live on our skin The mouth and pharynx contain many species of bacteria The vagina contains acid-producing bacteria Infection or Colonization With Microorganisms (cont.)

  6. The microorganisms normally living in or on your body Some are useful Many have no effect Pathogens cause disease All are capable of causing disease if your health and immunity are weakened Opportunistic pathogens Microflora

  7. True or False. All interactions between humans and microorganisms are detrimental. Question

  8. False Rationale:Some microorganisms perform important functions for their human hosts, like producing vitamins, assisting digestion, or preventing harmful pathogens from entering the host. Answer

  9. Prions • Small modified infectious host proteins • Abnormally shaped versions of your own proteins • Cause normal proteins to change their shape and become new prions • Can clump together and damage cells • Cause degenerative disease in the central nervous system (e.g., mad cow disease) Kinds of Infectious Agents

  10. Kinds of Infectious Agents (cont.) • Viruses • Protein coat surrounding nucleic acid core • Have no metabolic enzymes of their own • Insert their genome into a host cell’s DNA • Use that cell’s metabolic machinery to make new viruses

  11. Kinds of Infectious Agents (cont.) • Bacteria • Cells without membrane-bound organelles (prokaryotes) • Can live independently • Use infected organism for food and shelter

  12. Kinds of Infectious Agents (cont.) • Bacteria • Can produce toxins • Exotoxins are proteins released by bacteria • They damage or kill host cells • Endotoxins are parts of the bacterial cell wall • They cause host immune reactions

  13. Mycoplasmas, rickettsiae, chlamydiae • Smaller than bacteria • Mycoplasmas lack cell walls • Rickettsiae and chlamydiae have to live inside cells to metabolize, like viruses Kinds of Infectious Agents (cont.)

  14. Kinds of Infectious Agents (cont.) • Fungi • Most require a cooler temperature than human core body temperature • So most infections are on the surface of the body Tinea is a fungal infection of the skin

  15. Parasites • Protozoa: malaria, amoebic dysentery, giardiasis • Helminths: roundworms, tapeworms, flukes • Arthropods: ticks, mosquitoes, mites, lice, fleas Kinds of Infectious Agents (cont.)

  16. Parasites • Protozoa: malaria, amoebic dysentery, giardiasis • Helminths: roundworms, tapeworms, flukes • Arthropods: ticks, mosquitoes, mites, lice, fleas Kinds of Infectious Agents (cont.) giardia lamblia Trichomonas vaginalis

  17. Which pathogen is an intracellular parasite consisting of a protein coat surrounding a nucleic acid? • Prion • Virus • Bacteria • Protozoa Question

  18. Virus Viruses have no organized cellular structure like bacteria and protozoa. Viruses can only replicate inside another cell; prions cannot reproduce at all. Answer

  19. How many ways could you have become infected today? How could you have experienced: • Direct contact with a pathogen? • Ingestion of a pathogen? • Inhalation of a pathogen? • Contact with a zoonosis? • Contact with a nosocomial infection? • Contact with a fomite? Discussion:

  20. Symptomatology infection -Collection of signs and symptoms expressed by the host during the disease course. Also known as the clinical picture or disease presentation inflammatory and immune responses attack infective agent NONSPECIFIC: SPECIFIC: signs signs and and symptoms of symptoms of local damage and systemic inflammation inflammation

  21. A 5-year-old boy has an ear infection… • He complains of pain in his ear and cannot hear on that side. • When you look into his ear, you see a red, bulging eardrum with pus behind it. • He has a fever, sweats, and complains of joint aches. • Blood tests show an elevated white blood cell count. Question: • Use the model of symptomatology to classify these signs and symptoms. Scenario:

  22. What stage of an infection are you in? • How many people in the class are in: • The incubation stage? • The prodromal stage? • The acute stage? • The convalescent stage? • The resolution stage? How can you tell? Discussion Pathogen begins replication w/o recognizable symptoms Initial appearance of mild vague symptoms Host experiences maximum impact of the infection Containment of infection, progressive elimination of pathogen Total elimination of pathogen and signs

  23. -itis means • May or may not be due to infection • -emia means • Sepsis or septicemia means Terms for Infection and Damage inflammation in the blood bacterial toxins in the blood

  24. Make an infection more likely to cause disease • Toxins: exotoxins and endotoxins • Adhesion factors help infective organism stick to the body • Evasive factors help keep immune system from killing infective agent Virulence Factors

  25. True or False: Certain bacterial cells release proteins called endotoxins during growth. Question ?

  26. False Exotoxins are proteins; endotoxins contain no protein (they are composed of lipids and polysaccharides). Endotoxins are not released during bacterial cell growth. Answer

  27. A woman’s stomach contained the bacterium Helicobacter pylori… • For many years, the woman was healthy • Then she took on a new stressful job, moved, and began to care for her elderly parents • A few months later, she began to suffer stomach pains and vomited blood • She was diagnosed with a bleeding ulcer Scenario:

  28. Question: • How does each of these terms relate to her case? • Portal of entry • Site-specific pathogen • Opportunistic pathogen • Evasive factors • Invasive factors Scenario (cont.)

  29. After exposure to an infectious agent, the body produces antibodies Antibody titer rises IgM: rises during the acute phase, then falls IgG: remains elevated after the acute phase Serology

  30. A month-old baby is ill: • Serum analysis shows that she has IgG against HIV and IgM against Pneumocystis Question: • What inferences can you make? Scenario Crosses placenta Does not cross placenta Caused by protozoan that infects immunocompromised people

  31. We have more drugs to kill bacteria than to kill viruses, and more drugs to kill viruses than to eradicate prions Question: • Why has it been easier to develop antibacterial drugs than antiviral drugs? • Why not use antibacterial or antiviral drugs to destroy prions? Antibacterial and Antiviral Drugs

  32. Cell wall synthesis Protein synthesis Nucleic acid synthesis Bacterial metabolism Antibiotics Kill Bacteria By Targeting: Look for something different in bacteria from eukaryotes Peptidoglycan Ribosomal differences DNA sequence, polymerase, r. transcriptase Folic acid synthesis Bacteria Fight Back By: • Inactivating antibiotics • Changing antibiotic binding sites • Using different metabolic pathways • Changing their walls to keep antibiotics out

  33. Blocking viral binding to cells Blocking viral RNA or DNA synthesis Blocking production of the protein coats (capsids) of new viruses Antiviral Agents Kill Viruses By: Made as one long chain of AAs then cut with proteases Must have for replication Contains attachment proteins

  34. What type of infections are treated based upon the results of a Gram stain? • Fungal • Viral • Bacterial • Parasitic Question

  35. Bacterial Bacteria are commonly classified according to Gram stain. Gram-positive and gram-negative organisms are treated with specific antibiotics that target that type of infection. For example, penicillin targets gram-positive organisms. If the cause of bacterial infection is unknown, broad-spectrum antibiotics may be prescribed, targeting both gram-positive and gram-negative organisms. Answer