1-11 Commensalism vs. Pathology Flashcards
Define:
Mutualism
Commensalism
Parasitism
Mutualism (symbiosis): organism 1 (initiates interaction) benefits, organism 2 ALSO benefits
Commensalism: organism 1 benefits, organism 2 neither benefits nor is harmed.
Parasitism (in micro, pathogenesis): Organism 1 benefits, organism 2 is HARMED
Describe the condition under which a commensal microorganism can become a pathogen
Many commensal microorganisms are opportunistic pathogens, and can become pathogenic when they are in the wrong part of the body (out of their appropriate “container”), when the host is immunocompromised, or when the population balance among commensals is disrupted (e.g. due to antibiotic exposure).
Define normal flora
The normal flora are bacteria which are found in or on our bodies on a semi-permanent basis without causing disease
Human normal flora is mostly commensal.
Name two commensal microorganisms common in each system: Gastrointestinal Respiratory Reproductive Skin
Gastrointestinal System– Clostridium difficile, Escherichia coli
Respiratory System – Streptococcus pyogenes, Staphylococcus aureus
Reproductive System- Candida albicans, Lactobacillus acidophilus
Skin – Staphylococcus epidermidis
Define colony resistance and explain how it serves as an element of innate immunity
Colonization resistance is the process by which commensal bacteria help to prevent the colonization of foreign bacteria.
It is anti-pathogenic and nonspecific, and thusly is an important element in the nonspecific innate immunity.
Define ID50 and LD50
ID50 – The dosage needed to infect half of the host cells (used to determine how much is needed to cause disease).
LD50 – The dosage needed to kill half of the host cells (used to determine how much is needed to kill the host).
Define:
Obligate Intracellular Parasites
Facultative Intracellular Parasites
Obligate Intracellular Parasites – Parasites that can only propagate by using a cellular host.
Facultative Intracellular Parasites – Parasites that can propagate without a cellular host when necessary.
What are the 5 major activities of virulence factors?
- Survival in extreme environments
- adhesion
- immune evasion
- host cell takeover
- poisoning host
What are Types 3 & 4 secretion systems?
Used for host cell takeover
Type 3: injects toxin “injectosome”
Type 4: comparable but able to transport DNA in addition to proteins
Recite Koch’s Postulates
- Observe potential pathogen of sick animal
- Grow a pure culture of pathogen
- Infect a new animal from the culture (this is not done at a usual office visit)
- Observe same disease in new animal
- Culture the same potential pathogen from the new animal
If fulfilled, can say with certainty that the pathogen causes disease
What are exotoxins?
Involved in “poisoning of host” virulence factor. These are polypeptides secreted from the pathogen or injected into host cell by T3SS.
Common activities may include: profound toxicity may result from superantigenicity, interference with signal transduction, depolymerization of actin, or other acitvities
What the function of each subunit in A-B subunit structure?
A unit is the active toxic activity
B unit binds the host cell to deliver A
What is heat- or chemically inactivated exotoxin called?
What can this be used for?
Toxoid…useful as a vaccine
Are previous exposure or vaccination protective against endotoxins?
No-endotoxins are intrinsic to the surface of bacteria, cause immunogenic symptoms, and neither previous exposure NOR vaccination are protective against endotoxins
Endotoxin are cell wall components of which type of bacteria? (Gram+/-) and what is an example of one?
Gram -
LPS
