Chapter 14: Pathogenesis Of Infectious Diseases Flashcards
Explain the 4 periods or phases in the course of an infectious disease.
1) Incubation period- the time that elapses between arrival of the pathogen and the onset of symptoms.
2) Prodromal period- time during which the patient feels out of sorts but is not yet experiencing actual symptoms of the disease.
3) Period of illness- time during which patient experiences the typical symptoms associated with that particular disease. - communicable diseases are most easily transmitted during this phase.
4) Convalescent period- time during which the patient recovers.
List 4 reasons why an individual might not develop an infectious disease after exposure to a pathogen.
1) The microbe might land on an anatomic site where it is unable to multiply.
2) if a pathogen lands on a site where the specific receptor sites it attaches to are absent, it cannot multiply and cause damage.
3) Antibacterial factors that destroy or inhibit the growth of bacteria may be present.
4) Space and nutrients may be occupied by indigenous microflora.
5) Indigenous microflora may produce antibacterial factors (proteins called bacteriocins).
6) Individual’s nutritional and overall health status.
7) The person might be immune to a particular pathogen.
8) Phagocytic white blood cells may engulf and destroy the pathogen before it multiplies.
Differentiate between localized and systemic infections.
Localized- pathogens are contained at original site of infection.
Systemic- pathogen is spread throughout the body. may be carried to other parts of the body by way of lymph, blood, or in some cases, phagocytes.
Explain how acute diseases differ from subacute and chronic diseases.
Acute disease- has a rapid onset, usually followed by a relatively rapid recovery; measles, mumps, influenza
Chronic disease- an insidious onset and lasts a long time; tuberculosis, leprosy, syphilis
Subacute disease- having a sudden onset and developing into a long-lasting disease; subacute bacterial endocarditis- SBE
Differentiate between “symptoms” of a disease and “signs” of a disease and list examples.
Symptoms- subjectively perceived by patient; pain, ringing in the ears, blurred vision, nausea, dizziness, itching, chills
-symptomatic disease- patient is experiencing symptoms
-asymptomatic disease- patient is not experiencing symptoms
Signs- objective findings which are not perceived by the patient; during palpating, physician might discover a lump or enlarged liver (hepatomegaly) or spleen (splenomegaly), abnormal heart or breathing sounds, blood pressure, pulse rate, & laboratory results
Define and cite examples of latent infections.
Latent infection- disease that is lying dormant, not currently manifesting itself; herpes, genital herpes, shingles
Triggers- fever, sunburn, extreme cold, emotional stress
Differentiate between primary and secondary infections.
When one disease follows another.
Primary infection- first disease
Secondary infection- second disease cause by a different pathogen
List 6 steps in the pathogenesis of infectious disease.
1) Entry of pathogen into the body
2) Attachment of pathogen to some tissue(s) within the body
3) Multiplication of pathogen
4) Invasion or spread of the pathogen
5) Evasion of host defenses
6) Damage to host tissue(s)
Define virulence and virulence factors.
Virulence- capability of a microbe to cause a disease
Factors- phenotypic characteristics that enable microbes to be virulent
List bacterial structures that serve as virulence factors
Adhesins or ligands- molecules on a pathogen’s surface that recognize and attach to receptors on a host cell’s surface.
Bacterial Fimbriae (Pili)- long, thin, hairlike, flexible projections composed of proteins called pilin. They enable bacteria to attach to surfaces, including various tissues in the human body.
Capsules- protect bacteria from being phagocytized because WBCs cannot adhere to them.
Flagella- enable bacteria to invade areas of the body that nonflagellated bacteria cannot reach.
List bacterial exoenzymes that serve as virulence factors.
1) Necrotizing Enzymes- cause destruction of cells and tissues
2) Coagulase- causes clotting- protects bacteria against host defense mechanisms
3) Kinases- dissolve clots- to escape from clotting caused by host to trap pathogen
4) Hyaluronidase- breaks down hyaluronic acid (holds tissues together) enabling pathogen to invade deeper into tissues
5) Collagenase- breaks down collagen (the supportive protein in tendons, cartilage, and bones). Enables pathogen to invade into tissues
6) Hemolysins- enzymes that cause damage to RBCs. Bursting of RBCs provides pathogens with iron- needed by pathogen.
7) Lecithinase- breaks down lecithin in cells membranes- destructive to cell membranes, RBCs, and other tissues
Differentiate between endotoxins and exotoxins.
Endotoxins- component of the cells walls of Gram-negative bacteria. Can cause serious, adverse, physiologic effects such as fever and shock.
-pyrogens- substances that cause fever
-shock- resulting from very low blood pressure and inadequate blood supply to body tissues and organs
Exotoxins- poisonous proteins that are secreted by a variety of pathogens
List bacterial exotoxins and the diseases they cause.
1) Neurotoxins- affect the central nervous system; tetanus and botulism
2) Enterotoxins- affect the gastrointestinal tract; diarrhea, vomiting, and pseudomembranous colitis (damage to the lining of the colon)
3) Exfoliative toxin- causes the epidermal layers of skin to slough away (scalded skin syndrome)
4) Erythrogenic toxin- causes scarlet fever
5) Leukocidins- destroy WBCs
6) Diphtheria toxin- inhibits protein synthesis, kills mucosal epithelial cells and phagocytes and adversely affect the heart and nervous system.
7) Staphylococcus aureus TSST- 1- causes most cases of toxic shock syndrome
Describe mechanisms by which pathogens escape the immune response.
1) Antigenic Variation- the ability of some pathogens to periodically change their surface antigens
2) Camouflage and Molecular Mimicry- pathogens cover their surface with host proteins so that it will not be recognized as foreign. In mimicry, pathogen’s antigens closely resemble host’s antigens.
3) Destruction of Antibodies- some pathogens produce enzymes (IgA protease) that destroy IgA antibodies.
