Chapter 10 Infection PDF Lecture Notes

Chapter 10 Infection Copyright © 2019, Elsevier Inc. All rights reserved.  Emerging Infections  Infectious disease is a significant cause of death and morbidity because of  the reemergence of old infections thought to be controlled.  the emergence of pre...

Chapter 10 Infection Copyright © 2019, Elsevier Inc. All rights reserved.  Emerging Infections  Infectious disease is a significant cause of death and morbidity because of  the reemergence of old infections thought to be controlled.  the emergence of previously unknown infections.  the development of infections resistant to multiple antibiotics.  More than 40 unknown infections have arisen within 1 generation. Copyright © 2019, Elsevier Inc. All rights reserved. 2 Microorganism and Humans: A Dynamic Relationship  Mutual symbiotic relationship  Microorganism and human benefit  Normal microbiome Resident microorganisms are found in different parts of the body. Produces enzymes that help digestion. Produces antibacterial factors.  Prevents colonization by pathogens. Produces metabolites.  Vitamin K  B vitamins Copyright © 2019, Elsevier Inc. All rights reserved. 3  Clinical Infectious Disease  Incubation  Is the period from initial exposure to the onset of the first symptoms; could last from hours to years.  Prodromal  The occurrence of initial symptoms is often very mild with feelings of discomfort and tiredness.  Invasion  Invasion is farther and affects other body tissues.  Convalescence  Recovery occurs and symptoms decline, or the disease is fatal, or has a period of latency. Copyright © 2019, Elsevier Inc. All rights reserved. 4 Clinical Infectious Diseases (Cont.)  True pathogens: Bypass normal defenses and cause infection.  Infection is usually dependent on adequate numbers of microorganisms rather than a compromise of the host’s defenses. Copyright © 2019, Elsevier Inc. All rights reserved. 5 Clinical Infectious Diseases (Cont.)  Colonization  Infectious microorganisms: Exist in reservoirs (contaminated soil, contaminated water, breast milk), animals, or another human.  Are transmitted by: Direct transmission Indirect transmission: Vectors Droplet vs. airborne Vertical vs. horizontal  Microorganisms adhere to tissue through specific surface receptors. Copyright © 2019, Elsevier Inc. All rights reserved. 6 Clinical Infectious Diseases (Cont.)  Invasion  Invade surrounding tissues by evading the host’s defense mechanisms.  Multiplication  Warm and nutrient-filled environment of human tissue cause most microorganisms to multiply rapidly. Viral pathogens replicate within infected cells. Some bacteria are intracellular pathogens and replicate in macrophages and other cells.  Spread  May stay localized or enter other body areas; if the immune system is compromised, spreading is quick. Copyright © 2019, Elsevier Inc. All rights reserved. 7  Clinical Infectious Disease Question 1 A person arrives at the clinic and reports mild tiredness and discomfort after exposure to a family member with the flu. The nurse suspects the person is in the 1. convalescence period. 2. incubation period. 3. prodromal period. 4. invasion period. Copyright © 2019, Elsevier Inc. All rights reserved. 8  Clinical Manifestations of Infectious Disease  Are variable, depending on the pathogen.  Is caused directly by the pathogen or indirectly by its products.  Manifestations include fatigue, malaise, weakness, loss of concentration, generalized aching, and loss of appetite.  Fever  Is the hallmark of infection.  Body temperature is regulated at a higher level than normal. Exogenous pyrogens Endogenous pyrogens Copyright © 2019, Elsevier Inc. All rights reserved. 9 Factors Affecting Disease Development  Capacity of pathogen to cause disease  Communicability: Ability to spread from person to person  Immunogenicity: Ability to produce an immune response  Infectivity: Ability to invade and multiply in the host  Mechanism of action: How microorganism damages tissue  Pathogenicity: Ability to produce disease  Portal of entry: Route microorganism takes  Toxigenicity: Production of toxins  Virulence: Capacity to cause severe disease; potency Copyright © 2019, Elsevier Inc. All rights reserved. 10  Infectious Disease Classification  Endemic  Diseases with relatively high, but constant, rates of infection in a particular population  Epidemic  Number of new infections in a particular population that greatly exceeds the number usually observed  Pandemic  An epidemic that spreads over a large area such as a continent or worldwide Copyright © 2019, Elsevier Inc. All rights reserved. 11 Classes of Infectious Microorganisms  Bacteria  Fungi  Parasites  Protozoa  Viruses Copyright © 2019, Elsevier Inc. All rights reserved. 12  Bacterial Infections  True bacteria  Binary fission  Filamentous bacteria  Branching, mycelium-like structures  Spirochetes  Flexible, spiral, anaerobic  Mycoplasma  Smallest, simplest bacteria  Rickettsia  Intracellular parasites  Chlamydia  Intracellular parasites with complex life cycles Copyright © 2019, Elsevier Inc. All rights reserved. 13  Bacterial Infections (Cont.)  Gram-negative bacteria  Do not retain crystal violet dye in Gram staining process.  Lipopolysaccharide coat (endotoxin)  Gram-positive bacteria  Do retain crystal violet dye in Gram staining process. Copyright © 2019, Elsevier Inc. All rights reserved. 14  Bacterial Infections (Cont.)  Exotoxins: Enzymes released during growth  Damages cell membranes, activates second messengers, and inhibits protein synthesis.  Endotoxins: Contained in cell walls of gram- negative bacteria and released during lysis of bacteria  Is called pyrogenic bacteria because they activate inflammation and produce fever. Copyright © 2019, Elsevier Inc. All rights reserved. 15  Bacterial Infections (Cont.)  Produce toxins and extracellular enzymes to destroy phagocytic cells.  Coat the crystalline fragment (Fc) portion of an individual’s antibody, preventing complement activation or phagocytosis.  Degrade immune cells.  Bind and neutralize antibodies.  Evade complement.  Cause immune suppression.  Resistant: Alter surface molecules that express antigens. Copyright © 2019, Elsevier Inc. All rights reserved. 16  Bacterial Infections (Cont.)  Tissue damage from bacterial products, especially toxins or indirectly from infection or inflammation  Superantigens  Endotoxic shock  Staphylococcus aureus: Major cause of hospital- acquired (nosocomial) infections and antibiotic resistance  β-lactamase, an enzyme that destroys penicillin; more recently, bacteria developed a resistance to methicillin, called methicillin-resistant S. aureus (MRSA) Copyright © 2019, Elsevier Inc. All rights reserved. 17  Fungal Infections  Large microorganisms with thick, rigid cell walls  Mold, yeast, dimorphic  Disease caused by fungi: Mycosis  Disease transmitted by inhalation or contamination of wounds  Dermatophytes if infections invade skin, hair, or nails Copyright © 2019, Elsevier Inc. All rights reserved. 18 Fungal Infections (Cont.) Copyright © 2019, Elsevier Inc. All rights reserved. 19  Fungal Infections (Cont.)  Systemic infection is usually from immunosuppression.  Pneumocystis carinii was reclassified as a fungus and renamed P. jiroveci.  Adapt to the host environment.  Wide temperature variations, low oxygen, alkaline pH  Suppress the immune defenses. Copyright © 2019, Elsevier Inc. All rights reserved. 20  Fungal Infections (Cont.)  Some fungi survive phagocytosis by replicating in the phagosome or inhibiting lysosomal enzymes.  Fungi encapsulate, alter antigen expression, and stimulate immunosuppressive cytokines to resist phagocytosis.  Tissue damage is from fungal enzymes and indirectly from inflammation. Copyright © 2019, Elsevier Inc. All rights reserved. 21  Fungal Infections (Cont.)  Candida albicans: Is the most common fungal infection.  Resides in skin, gastrointestinal tract, mouth, and vagina.  Local defense mechanisms and microbiome produce antifungal agents.  Remains localized if the immune system is intact; if the immune system is compromised, then the infection can become systemic. Copyright © 2019, Elsevier Inc. All rights reserved. 22 Fungal Infections (Cont.) 23  Parasitic and Protozoan Infections  Parasites range from unicellular protozoa to large worms.  Parasitic worms (helminths) Intestinal and tissue nematodes (e.g., hookworm, roundworm) Flatworms (e.g., liver fluke, lung fluke, tapeworm)  Most common parasitic infections in US  Toxoplasma gondii  Trichomonas vaginalis Copyright © 2019, Elsevier Inc. All rights reserved. 24  Parasitic and Protozoan Infections (Cont.)  Are rarely transmitted from human to human; are transmitted mainly through vectors.  Malaria by mosquito bites  Trypanosomes by the tsetse fly  Leishmania spp. by sand fleas  Others found in contaminated water or food (e.g., Giardia lamblia). Copyright © 2019, Elsevier Inc. All rights reserved. 25  Parasite Invasion  Extracellular  GI tract  Vagina (STI)  Skin (bites)  Intracellular  Ingestion of contaminated food/water  Bites from insect vectors  Tissue damage caused by parasites is secondary to release of enzymes that destroy surrounding extracellular matrix and tissue. Copyright © 2019, Elsevier Inc. All rights reserved. 26  Response to Parasitic Infection  Individual’s immune/inflammatory response  Physical loss in tissue or organ  Immune hypersensitivity reaction Copyright © 2019, Elsevier Inc. All rights reserved. 27 Parasite Blocking of Immune Response  Antibody-mediated complement activation  Effective against several parasites  Pathogen-specific and nonspecific immune suppression Copyright © 2019, Elsevier Inc. All rights reserved. 28  Malaria  Malaria: Is the most common infection worldwide.  Is transmitted through the bite of an infected Anopheles mosquito.  Parasite enters the bloodstream, survives in the liver, and invades the parenchymal cells.  After several rounds of division, the liver cell ruptures, and thousands of parasites enter the blood, infecting the red blood cells. Copyright © 2019, Elsevier Inc. All rights reserved. 29  Parasitic and Protozoan Infections Question 2 Which information is correct regarding parasitic infections? 1. These types of infections attach through pili (fimbriae). 2. C. albicans is an example of a parasitic infection. 3. Parasitic infections are transmitted from human to human. 4. Malaria is a common parasitic infection. Copyright © 2019, Elsevier Inc. All rights reserved. 30  Infectious Viruses https://www.freepik.com/free-photos-vectors/virus 31  Infectious Viruses  Basic structure is the virion (nucleic acid surrounded by the capsid).  Is classified by the nucleic acid in the virion (ribonucleic acid [RNA] or deoxyribonucleic acid [DNA]), whether it is single stranded (ss) or double stranded (ds), and whether it uses the enzyme reverse transcriptase for replication.  Viral diseases: Are the most common affliction of humans and include the common cold, cold sores, hepatitis, human immunodeficiency virus (HIV), and several types of cancer. Copyright © 2019, Elsevier Inc. All rights reserved. 32  Infectious Viruses (Cont.)  Viruses: Intracellular parasites  Life cycle: Completely intracellular  Attaches or binds to the host cell via protein receptors.  Penetrates the host cell.  Releases genetic information into the host cytoplasm. RNA viruses enter the host nucleus. Produce messenger RNA (mRNA) (new viral material).  May produce provirus DNA (retroviruses, HIV). DNA viruses enter the host nucleus.  May integrate into the host DNA; may make mRNA. Copyright © 2019, Elsevier Inc. All rights reserved. 33  Infectious Viruses (Cont.)  Life cycle  Translation of mRNA results in the production of viral proteins.  For enveloped viruses, new virions are released through budding.  Viral DNA is integrated in the host cell and transmitted to daughter cells by mitosis. Copyright © 2019, Elsevier Inc. All rights reserved. 34  Infectious Viruses (Cont.)  Stages of viral infection (1) Enveloped viruses bind to receptors. (2) The virion particle undergoes receptor-mediated endocytosis. (3) The endosome fuses with lysosomes. (4) Budding and release of viral nucleic acid into the cytoplasm. Copyright © 2019, Elsevier Inc. All rights reserved. 35  Infectious Viruses (Cont.)  Viruses rarely produce toxins.  Viral infection symptoms are mild.  Fever, aches, nausea  Some viruses rapidly proliferate.  Norovirus, rotovirus, Ebola, Marburg, hantavirus  Interferons are effective against many viruses.  Viruses are sensitive to complement activation. Copyright © 2019, Elsevier Inc. All rights reserved. 36  Infectious Viruses (Cont.)  Harmful effects  Inhibition of DNA, RNA, or protein synthesis  Disruption of lysosomal membranes  Promotion of cell apoptosis  Fusion of adjacent cells (giant cells)  Transformation into cancer cells  Alteration of antigenic properties (immune attacks normal cells) Copyright © 2019, Elsevier Inc. All rights reserved. 37  Infectious Viruses (Cont.)  Influenza: Is highly infectious.  Virions attach to respiratory epithelial cells and enter by endocytosis.  May be fatal for the very young and the very old; it is seasonal.  Surface proteins undergo change each year.  Can have antigenic drift or mutation. Mutation of genes that express surface molecules  Can have antigenic shift. Recombination into a new virus from two different species Copyright © 2019, Elsevier Inc. All rights reserved. 38 Infectious Viruses (Cont.) 39  Acquired Immunodeficiency Syndrome  Acquired immunodeficiency syndrome (AIDS) is caused by the virus HIV.  Depletes the body’s T helper (Th) cells.  Is susceptible to life-threatening infections and cancer.  Incidence Worldwide  Is and remains a major cause of morbidity and mortality.  The epicenter of the AIDS pandemic is Africa. United States  In 2014, 21,000 new cases reported.  Approximately 650,000 people have died from AIDS since early 1980s. Copyright © 2019, Elsevier Inc. All rights reserved. 40  Acquired Immunodeficiency Syndrome (Cont.)  Bloodborne pathogen is present in body fluids (e.g., blood, vaginal fluid, semen, breast milk).  Routes of transmission  Blood or blood products, intravenous drug use, heterosexual and homosexual activity, and maternal-child transmission before or during birth  Two types: Both are retroviruses  HIV-1  HIV-2 Copyright © 2019, Elsevier Inc. All rights reserved. 41  Acquired Immunodeficiency Syndrome (Cont.)  RNA virus (retrovirus)  Stores genetic material on two copies of RNA rather than the usual dsDNA.  Carries an enzyme, reverse transcriptase, that creates a dsDNA version of the virus.  Integrase inserts new DNA into the infected cell’s genetic material. May be dormant: No problems develop. May activate: Many problems develop; new DNA becomes part of the cell’s genetic material and accelerates apoptosis and shedding of infectious HIV. Copyright © 2019, Elsevier Inc. All rights reserved. 42  Acquired Immunodeficiency Syndrome (Cont.)  Clinical manifestations  Serologically negative, serologically positive but asymptomatic, early stages of HIV, or AIDS  Window period: Infectious but asymptomatic  Fatigue, headache, muscle aches, fever  May be asymptomatic for years. Copyright © 2019, Elsevier Inc. All rights reserved. 43 Acquired Immunodeficiency Syndrome (Cont.) 44  Acquired Immunodeficiency Syndrome (Cont.)  Diagnosis  Uses various clinical conditions and laboratory tests.  Atypical or opportunistic infections and/or cancer  CD4+ T-cell numbers are at or below 200 cells/µL (depending on age). Copyright © 2019, Elsevier Inc. All rights reserved. 45  Acquired Immunodeficiency Syndrome (Cont.)  Treatment: Antiretroviral therapy (ART)  Three or more drugs: Usually two drugs target reverse transcriptase (inhibits reverse transcriptase) and one is from a different class of drugs.  Does not cure; rather, it slows progression.  Prevention is currently not possible as no vaccine has proven effective. Link to video on HIV & AIDS Copyright © 2019, Elsevier Inc. All rights reserved. 46 Acquired Immunodeficiency Syndrome (Cont.) 47  Acquired Immunodeficiency Syndrome Question 3 A person who is HIV positive is hospitalized with pneumonia caused by Pneumocystis jiroveci. The nurse understands that this development indicates the person 1. has adequate amounts of Th cells. 2. is serologically positive for asymptomatic HIV disease. 3. is in the early stages of HIV disease. 4. has progressed from HIV to AIDS. Copyright © 2019, Elsevier Inc. All rights reserved. 48 Pediatric Acquired Immunodeficiency Syndrome and Central Nervous System Involvement  Presence of passive maternal antibody limits testing of HIV antibodies in infants up to 18 months.  Central nervous system (CNS) is particularly vulnerable.  Developmental delays; loss of intellectual abilities  Impaired brain growth or acquired microcephaly  Motor deficits Copyright © 2019, Elsevier Inc. All rights reserved. 49  SARS CoV-2  Link to video on Structure and Pathogenesis of SARS-CoV-2 50  Countermeasures Against Pathogens  Environmental infection control measures  Antimicrobials  Prevent growth (bacteriostatic) or directly kill (bactericidal) microorganisms. Inhibit production and function of the cell wall. Block DNA replication. Inhibit protein synthesis. Interfere with folic acid metabolism.  Can develop resistance to some antimicrobials.  Antivirals: Are sometimes less successful because viruses use host enzymes. Copyright © 2019, Elsevier Inc. All rights reserved. 51  Countermeasures Against Pathogens (Cont.)  Antibiotic resistance  CDC: urgent, serious, concerning  Horizontal gene transfer  Enzymatic inactivation of antibiotics  Aminoglycoside-modifying enzymes (AMEs)  Multi-drug resistant transporters (MDRs)  Proteins that prevent antibiotic cell access  Target bypass  Resistance mechanism Link to video on antibiotic resistance Copyright © 2019, Elsevier Inc. All rights reserved. 52  Countermeasures Against Pathogens (Cont.)  Methicillin-resistant Staphylococcus aureus (MRSA)  International healthcare crisis  Over use of antibiotics/not completing antibiotic regimen  Fusidic acid: binds to ribosome and prevents protein synthesis  Old treatment revisited: bacteriophages Viruses that infect bacteria Copyright © 2019, Elsevier Inc. All rights reserved. 53  Countermeasures Against Pathogens (Cont.)  Active immunization: Vaccines  Prevent the initiation of disease.  Do not last as long as infection-produced immunity. Need boosters  Viral vaccines  Attenuated: Weakened live virus (measles, mumps, and rubella [MMR], varicella, polio [oral], rotavirus)  Inactivated: Killed virus (hepatitis A, polio [injected], influenza)  Recombinant: Hepatitis B, human papillomavirus (HPV) Link to Video on Novel Vaccines for SARS-CoV-2 Copyright © 2019, Elsevier Inc. All rights reserved. 54  Countermeasures Against Pathogens (Cont.)  Bacterial vaccines  Conjugated (to carrier proteins) Increased immunogenicity Haemophilus influenzae type B (Hib)  Toxoids Vaccines against bacterial toxins (diphtheria, tetanus, and pertussis [DTaP], diphtheria and tetanus [DT])  Extracted capsular polysaccharides: Dead bacteria Meningococcal, pneumococcal Copyright © 2019, Elsevier Inc. All rights reserved. 55  Countermeasures Against Pathogens Question 4 A nurse is asked how antibiotics work. How should the nurse reply? One of the actions of antibiotics includes 1. protection of the bacterial cell wall. 2. inhibition of protein synthesis. 3. enhancement of DNA replication. 4. support for folic acid synthesis. Copyright © 2019, Elsevier Inc. All rights reserved. 56  Countermeasures Against Pathogens  Passive immunotherapy  Preformed antibodies are administered to individuals.  Is useful for hepatitis A and B, Ebola, and rabies. Copyright © 2019, Elsevier Inc. All rights reserved. 57