Transcript Ch14
Essentials of Pathophysiology CHAPTER 14 MECHANISMS OF INFECTIOUS DISEASE PRE LECTURE QUIZ (TRUE/FALSE) Creutzfeldt-Jakob disease and mad cow disease are examples of prion-associated diseases. F Viruses are capable of replication outside of a living cell. T The term portal of entry refers to the process by which a pathogen enters the body. F Some fungi are members of normal human microflora. F All organisms cause infectious illness in humans. T PRE LECTURE QUIZ Acute Infections that develop in patients while they are hospitalized are called _________________. –itis 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. Nosocomial Parasites Symptomatology INFECTION OR COLONIZATION WITH MICROORGANISMS “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 (CONT.) 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 MICROFLORA 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 QUESTION True or False. All interactions between humans and microorganisms are detrimental. ANSWER False Rationale: Some microorganisms perform important functions for their human hosts, like producing vitamins, assisting digestion, or preventing harmful pathogens from entering the host. KINDS OF INFECTIOUS AGENTS 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 (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 KINDS OF INFECTIOUS AGENTS (CONT.) Bacteria Cells without membranebound organelles (prokaryotes) Can live independently Use infected organism for food and shelter 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 KINDS OF INFECTIOUS AGENTS (CONT.) 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.) 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 KINDS OF INFECTIOUS AGENTS (CONT.) Parasites Protozoa: malaria, amoebic dysentery, giardiasis Helminths: roundworms, tapeworms, flukes Arthropods: ticks, mosquitoes, mites, lice, fleas KINDS OF INFECTIOUS AGENTS (CONT.) Parasites Protozoa: malaria, amoebic dysentery, giardia lamblia giardiasis Helminths: roundworms, tapeworms, flukes Arthropods: ticks, mosquitoes, mites, lice, fleas Trichomonas vaginalis QUESTION Which pathogen is an intracellular parasite consisting of a protein coat surrounding a nucleic acid? a. Prion b. Virus c. Bacteria d. Protozoa ANSWER Virus Viruses have no organized cellular structure like bacteria and protozoa. Viruses can only replicate inside another cell; prions cannot reproduce at all. b. DISCUSSION: 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? 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 SPECIFIC: signs and symptoms of local damage and inflammation NONSPECIFIC: signs and symptoms of systemic inflammation SCENARIO: 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. DISCUSSION What stage of an infection are you in? How many people in the class are in: The incubation stage? Pathogen begins replication w/o recognizable symptoms The prodromal stage? Initial appearance of mild vague symptoms The acute stage? Host experiences maximum impact of the infection The convalescent stage? Containment of infection, progressive elimination of The resolution stage? pathogen Total elimination of pathogen How can you tell? and signs TERMS FOR INFECTION AND DAMAGE -itis means May inflammation or may not be due to infection -emia means in the blood Sepsis or septicemia means bacterial toxins in the blood VIRULENCE FACTORS 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 QUESTION True or False: Certain bacterial cells release proteins called endotoxins during growth. ? ANSWER False Exotoxins are proteins; endotoxins contain no protein (they are composed of lipids and polysaccharides). Endotoxins are not released during bacterial cell growth. SCENARIO: 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 (CONT.) Question: How does each of these terms relate to her case? Portal of entry Site-specific pathogen Opportunistic pathogen Evasive factors Invasive factors SEROLOGY 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 SCENARIO A month-old baby is ill: Serum analysis shows that she has IgG against HIV and IgM against Pneumocystis Does not cross placenta Question: What inferences can you make? Crosses placenta Caused by protozoan that infects immunocompromised people ANTIBACTERIAL AND ANTIVIRAL DRUGS • 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? ANTIBIOTICS KILL BACTERIA BY TARGETING: Look for something different in bacteria from eukaryotes Cell wall synthesis Peptidoglycan Ribosomal differences Protein synthesis Nucleic acid synthesis DNA sequence, polymerase, r. transcriptase Bacterial metabolism Folic acid synthesis Bacteria Fight Back By: • Inactivating antibiotics • Changing antibiotic binding sites • Using different metabolic pathways • Changing their walls to keep antibiotics out ANTIVIRAL AGENTS KILL VIRUSES BY: Made as one long chain of AAs then cut with proteases Blocking viral binding to cells Blocking viral RNA or DNA synthesis Blocking production of the protein coats (capsids) of new viruses Must have for replication Contains attachment proteins QUESTION What type of infections are treated based upon the results of a Gram stain? a. Fungal b. Viral c. Bacterial d. Parasitic ANSWER 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. c.