Host-parasite Interactions Flashcards
Do you have the same NF in your nose & on your foot?
No, the environments are different & so are the NF
What is indigenous flora?
Microorganisms commonly found on or in healthy people
What can the environments be for normal flora?
Supportive or selective
What are two synonyms for indigenous flora?
Normal flora
Resident flora
What is transient flora?
Bacteria that is occasionally there
What is parasitism?
A relationship in which one organism is benefitted & one is harmed
What is commensalism?
A relationship in which one organism benefits & the other is not harmed
What is symbiosis?
A relationship in which both organisms benefit
What is a carrier?
A person or animal that has a gene or a bacteria/pathogen but is not harmed
May be acute or chronic
What are the 4 components of host-parasite interactions?
Encounter & entry
Colonization & entry
Invasion & dissemination
Outcome
What happens during encounter & entry?
Pathogen encounters & colonizes host surfaces
What happens during colonization & entry?
Pathogen multiplies & breaches host surfaces
What occurs during invasion & dissemination?
Pathogen invades deeper tissues & disseminates
Encounters inflammatory & immune responses
What occurs during the outcome of host-parasite interactions?
Pathogen completes cycle
- leaves host
- destroys host
- remains in latent state
- is destroyed by host
What are the stages of host-parasite interaction from beginning to end?
Incubation stage Prodromal stage Clinical stage Stage of decline Convalescent stage
What are factors that affect colonization?
Nutritional status of site & host Oxidation/reduction potentials Antibody/antibacterial substances pH Other organisms Age of host Diseases that cause host to be immunocompromised Drug or antibiotic effects
What are the most common flora/microorganisms found on the skin?
Candida spp Micrococcus spp Staphylococcus spp Clostridium Diptheroids
What are the different types of pathogen infection?
Iatrogenic infection
Nosocomial infection
What is an iatrogenic infection?
Infection that follows a medical intervention
-post catheter causing UTI
What is a nosocomial infection?
Infections acquired in a health care setting
What is a pathogen?
A microbe causing disease in a susceptible host
What does virulence mean?
The strength or dangerousness of a pathogen
What are the degrees of pathogenicity?
Infective dose
Severity of disease
What does infective dose mean in regards to degree of pathogenicity?
How much bacteria there needs to be for one to get infected
What does severity of disease mean in regards to degree of pathogenicity?
How sick is one going to get
What are the factors of virulence of a pathogen?
Capsules Toxins Enzymes - catalase, coagulase, etc. Cell wall receptors Pili
What are the 7 steps in the invasion process?
Attachment/adherence Proliferation Virulence factors Tissue damage & inflammation Tissue damage by toxins Invasion Dissemination
What are attachment factors of pathogens?
Pili
Adherence proteins - adhesins
What are factors of pathogens that cause tissue damage & inflammation to the host?
Enzymes - coagulase, collagenase, hyaluronidase, lipase, elastase
Toxins - exotoxin & endotoxin
What is an endotoxin?
Part of the cell wall
LPS gram negatives
Released at death of bacteria
Can be life threatening
What is an exotoxin?
Composed of 2 units
Gram-positive & gram-negative
Extrachromosomal genes
What are the different routes of transmission of pathogens?
Airborne -> fomites Food & water Cuts & bites -> animals Arthropods - typhus, malaria Zoonoses - ebola, lyme
What are types of host resistance factors?
Physical barriers Cleansing mechanisms Antimicrobial substances of the host Indigenous microbial flora Phagocytes/phagocytosis Inflammation Immune response
What are physical barriers that allow for host resistance & what do they do?
Skin - mechanical barrier; sheds
When compromised by wound or disease, it is not effective
Very few organisms can penetrate intact skin
Antimicrobial substances of the host include what?
Fatty acids in stomach HCl in stomach Secretory IgA in mucous secretions are opsonins & fix complement Lysozyme Antibodies Beta lysins Combination of antibody, complement, lysozyme, & beta lysin Interferon
Where are lysozymes found?
Tears Serum Tissue fluids Breast milk Saliva Sweat
What do beta lysins do?
Act as gram positive organisms
What are cleansing mechanisms that the body does to rid itself of pathogens?
Crying Sloughing Swallowing Flushing Blinking Coughing Expectorating
How is indigenous microbial flora protective?
Produces bacteriocins to inhibit other bacterial growth
Produces restriction enzymes that destroy DNA of other bacteria
Compete for nutrients & space
Metabolic byproducts may cause hostile environment for other bacteria
What are the two types of phagocytes found in the body?
Neutrophils & macrophages
What do neutrophils do?
Pack things into lysosomes as granules
Are receptors for complement
What do macrophages do?
Act as monocytes
Are part of specific & nonspecific immunity
What is complement?
Metabolic burst & secretion of lysosomes into a phagosome
What are the parts of phagocytosis?
Chemotaxis
Attachment
Ingestion
Killing
What is chemotaxis?
Movement toward the bacteria
What is the attachment component of phagocytosis?
Facilitated by antibodies & complement
Flavor coating - opsonization
Bacterial capsules defend against attachment
What ingestion in phagocytosis?
Ingestion into phagosome
Lysosome fusion & degranulation
What is killing in phagocytosis?
Increase in metabolic activity of the cell
Called respiratory or metabolic burst
Increased glycolysis, O2 use, production of lactic acid & hydrogen peroxide that diffuses into the phagosome
What are intracellular survivors?
Organisms that survive killing attempt & multiply within the cells
What is inflammation?
Increase in phagocytic cells to the site
The release of mediators of inflammation causes what?
Erythema due to greater blood flow
Edema from increased vascular permeability
Phagocytosis leads to what?
Pus
Inflammation is ____ & _____.
Cleanup & repair
What are the two types of immunity?
Innate & adaptive/specific immunity
What happens in innate immunity?
Physical & chemical barriers - skin, tears, cells, etc. Blood proteins Cells eg. neutrophils & macrophage Previous exposure not required Rapid response
Adaptive immunity consists of what?
Antibodies produced to antigen stimulation
Produced by lymphocytes
Works with the innate system - antibodies work with complement
Response has immunologic memory, so that subsequent encounters with that antigen stimulate increasingly effective & specific defense
Lymphocyte subsets originate from where?
Bone marrow
When lymphocytes mature, they reside where?
Thymus
Lymph nodes
Spleen
What are the types of lymphocyte subsets?
T cells
B cells
Where are T cells derived from & what kind of immunity are they involved in?
Thymus derived
Cellular immunity
Where are B cells derived from & what type of immunity are they involved in?
Bone marrow derived
Humoral (body fluid - antibody production) immunity
T & B cells have different what?
Different sets of cell surface receptors
In specific humoral response, what happens?
Antigen binding to specific cell surface receptor results in clonal proliferation of lymphocytes that produce specific antibodies
What are antibodies named by?
The heavy chain
What order are antibodies are listed in order of concentration in the blood stream?
IgG IgA IgM IgD IgE
What does Ig stand for or mean?
Antibody
What is the percent serum Ig of IgG?
˜75% serum Ig
What is the half life of IgG?
3-4 weeks
What is the molecular weight of IgG?
150,00 MW
How many active sites are on IgG?
2
What is the percent Ig serum that IgM makes up?
˜10-15%
How long is the half life of IgM?
5 days
Does IgG cross the placenta?
Yes
Does IgM cross the placenta?
No
What is the molecular weight of IgM?
900,00
How many subunits make up IgM?
5 basic subunits - pentamer, linked by J chain
What is the percentage that IgA makes up?
˜15-20% serum Ig
Where is IgA usually found?
In body secretions, saliva tears, intestinal secretions
What is IgA composed of?
2 subunits similar to IgG linked by J chain & secretory component
What is IgE involved in?
Parasitic infections & allergies
What time does IgM peak at (weeks)?
1-2 weeks
When does IgG become detectable?
After IgM & increases for about 1 month
During the second exposure what happens?
Rapid increase
Longer elevation
Anamnestic response
What type of lymphocytes are involved in cell mediated immune response?
T lymphocytes
What happens during cell mediated immune response?
Bind antigen, activate, cell division -> production of lymphokines
What do lymphokines do?
Work by direct cell to cell contact or act with macrophage
What type of pathogens invoke cell mediated immune response?
Intracellular bacterial pathogens
What does the clinical lab department of serology use to date infections?
Measurement of IgG, IgA, & IgM
How does the clinical lab department of serology detect antibodies?
Uses titers to detect levels of specific antibodies
What is a titer?
The concentration of an antibody in the serum
What are strategies for prevention of infectious disease?
Epidemiology Prevent transmission Control bacteria reservoirs Minimize risk Washing hands
What types of strategies are used minimize disease?
Immunization - active/passive
Antimicrobial thearapy
Endemic
One area
Epidemic
Large number of patients that are infected than expected
Pandemic
Epidemic but spreading through a large region
Incidence rate
How fast its going - number of new cases in a time period
Prevalence
How many cases there are
Index case
First case known of a condition
Morbidity
How many people became sick
Mortality
How many have died
Incubation period
Period between infection & first signs of symptoms
