Chapter 14-16 Quiz Flashcards
Describe the 4 types of symbiosis
- Mutualism - both benefit
- Commensalism - 1 benefits, other neither benefits or harmed
- Parasitism - 1 benefits, 1 harmed
- Ammensalism - 1 harmed, other neither benefits nor harmed
Describe resident vs. transient microbiota
Resident microbiota remain a part of the normal microbiota for most of a person’s life.
Transient microbiota remain in the body for only a few hours to a few months.
Describe the concept of microbial antagonism
Normal microbiota uses nutrients, take up space, and release toxic byproducts, making it less likely that pathogens can compete well enough to establish and produce disease.
List 4 mechanisms by which normal microbiota can become pathogenic (opportunistic pathogens)
- Immune suppression
- Changes in normal microbiota (microbial antagonism)
- Introduction into an unusual site (eg. E. coli in urinary tract)
- Stressful conditions
Three types of reservoirs of infection in humans
- Zoonoses - animal host to humans
- Human carriers
- Non-living reservoir (food, water soil, etc)
List 4 portals of entry to the human body for invading pathogens
- Skin
- Mucous membranes
- Placenta
- Parenteral (under skin)
What is the basic definition of disease
Host is harmed; normal functioning is disrupted.
Describe the difference between infection and disease
Infection is the invasion of a pathogen. Disease only results if the pathogen multiplies sufficiently to adversely affect the body.
Describe the difference between signs and symptoms
Signs are objective; measurable or observable by others.
Symptoms are subjective; only felt by patient.
Define a syndrome
A group of signs and symptoms that characterize a condition or disease.
State Koch’s Postulates
- Suspected agent must be present in every case of the disease.
- Agent must be isolated and grown in pure culture.
- Cultured agent must cause disease when inoculated into healthy, susceptible host.
- The same agent must be found in the diseased host.
What it the difference between pathogenicity and virulence?
Pathogenicity is the CAPACITY to cause disease.
Virulence is the DEGREE of pathogenicity (i.e., relative ability of a pathogen to cause disease)
Define “virulence factors” and list 4.
Virulence factors are any TRAIT that enables a pathogen to cause disease.
- Adhesion
- Extracellular enzymes (hyaluronidase, collagenase allow invasion of DEEPER tissues)
- Toxins (exotoxins, endotoxins)
- Antiphagocytic factors
Examples of exotoxins
Cytotoxins, Neurotoxins, Enterotoxins, Hemolysins, Leukocidins
What are the effects when Lipid A is released in the body?
- Triggers release of cytokines
- Activates complement cascade
- Activates coagulation cascade
Name the 5 stages of infectious disease
- Incubation (no signs)
- Prodromal (mild, general signs/symptoms)
- Illness (full blown signs/symptoms)
- Decline
- Convalescence
Three modes of disease transmission
- Contact transmission
- Vehicle transmission
- Vector transmission
Three types of contact transmission
- Direct contact
- Indirect contact (fomites)
- Droplet (within 1 meter and close in time)
Three types of transmission by vehicles
Waterborne, airborne, foodborne
Two types of transmission by vectors
Biological (arthropods)
Mechanical (on insect bodies)
What is the term for an infection that is the direct result of a medical procedure
Iatrogenic
Exogenous vs. Endogenous infection
Exogenous infections are infections from a source other than the patient.
Endogenous infections are infections from patients’ own microflora.
Three types of epidemiological studies
- Descriptive epidemiology - Collect info during outbreak, attempt to find index case, break chain of transmission
- Analytical Epidemiology - Usually retrospective, to try determine cause of outbreak (tobacco and lung cancer)
- Experimental epidemiology - tests a hypothesis about the cause of a disease. Prospective, case controlled experiments
Incidence vs. Prevalence
Incidence is the number of new cases.
Prevalence is the number currently infected; cumulative.
Endemic vs. Epidemic vs. Pandemic vs. Sporadic
Endemic - occurs at a relatively stable incidence
Sporadic - only a few scattered cases occur
Epidemic - increase in number of cases over historic
Pandemic - epidemic occurs simultaneously on more than one continent
Common-source epidemic vs. propagated epidemic
In a common-source epidemic, there is no person to person spread (e.g., food poisoning). The number of incidence tend to spike then diminish quickly.
In a propagated epidemic (e.g., common cold), the number of incidence tend to increase more gradually and take longer to decrease.
Describe the first, second, and third lines of defense against pathogens
First line of defense is nonspecific and includes physical barriers, chemical barriers, mucous membranes.
Second line of defense is nonspecific and includes phagocytosis, complement, interferon, inflammation, fever.
Third line of defense is specific and includes lymphocytes, antibodies.
Which of the leukocytes is the major phagocytic cell
Neutrophils (a granulocyte)
Name the different types of leukocytes
Granulocytes: Neutrophils, Eosinophils, Basophils
Agranulocytes: Lymphocytes, Monocytes, NK cells
What is the major role of monocytes
Monocytes leave the blood by diapedesis and mature into MACROPHAGES, which are phagocytic cells of the second line of defense. Include resident and migrating macrophages.
Components of the second line of defense
- Phagocytosis
- Extracellular killing by leukocytes
- Specialized receptors recognize invaders. Toll-like receptors and NOD proteins recognize PAMP (pathogen-associated molecular patterns, s/a LPS, peptidoglycan, viral double stranded RNA)
- Nonspecific chemical defenses. Interferons and complement
- Inflammation
- Fever
Describe the two major phagocytes
- Neutrophils are the most abundant WBC and are very active phagocytes that eat bacterial and small particles. Migrate quickly.
- Macrophages migrate more slowly and eat cell debris and bacteria.
Three ways of avoiding death by phagocytosis
- Chemotaxis: don’t produce chemoattractants
- Adherence and ingestion: antiphagocytic capsule or proteins that interfere with adherence
- Digestion: Escape phagosome, prevent lysosomal fusion, survive inside phagolysosome
How to NK cells kill
NK cells are lymphocytes that act mostly non-specifically.
Recognize body cells with reduced MHCI.
Mode of action is extracellular killing via perforin-granzyme pathway. Poke holes in cell membranes and triggers cascade.
Which leukocyte attacks parasites
Eosinophils
Three major functions of the complement system
- OPSONIZE microbes for phagocytosis
- Enhance INFLAMMATION
- Lyse invading microbes through formation of Membrane Attack Complex (MAC)
Three ways to activate complement
- Alternative pathway
- Classical pathway
- Lectin pathway
Complement activation is carried out by which enzyme
C3 convertase
What are the components of C3 convertase
C3b + Bb
