Module 7: Parasites/Infectious Diseases Flashcards
Define parasitism, give 2 examples.
Relationship that only benefits one organism - the parasite. Ex. giardia lamblia, H1N1
Define mutualism, give an example.
Relationship that provides reciprocal benefits for both organisms. Ex. vaginal flora
Define commensalism.
One organism uses another, often larger, organism for nutrients, habitat, locomotion. Has no effect on the host.
What are two ways that commensal microbes on our microbiome can benefit us.
- preventing colonization by more pathogenic species
- producing metabolites used by host ex. B12
Define nonpathogen and virulence.
Nonpathogen: microorganism that does not cause disease, ex. flora
Virulence: Quantitative ability of an agent to cause disease.
Differentiate between primary pathogens and opportunistic pathogens.
Primary pathogen: causes disease in otherwise healthy people
Opportunistic pathogen: agent capable of causing disease only when host’s resistance is impaired
What are the four stages of infectious disease? Summarize briefly.
Incubation: time between exposure and appearance of symptoms.
Prodrome: nonspecific symptoms
Specific-Illness: characteristic features of disease occr
Recovery: symptoms resolve, health is restored
What are the three potential outcomes post-infection?
- chronic carriers
- latency
- cleared
What are the 5 aspects of pathogenesis?
- colonization/transmission
- adherence
- invasiveness
- toxins
- ability to evade immune response
What occurs during colonization/transmission?
Pathogens colonize host tissues, usually in contact with external environment ex. skin, resp tract, GI
What are the three methods of transmission in humans? Three methods when animals involved?
HUMAN
1. respiratory/salivary
2. fecal-oral
3. venereal
ANIMAL
1. vector (ex. malaria)
2. vertebrate reservoir (ex. rabies)
3. vector-vertebrate reservoir (ex. plague)
What does ID50 mean? LD50?
ID50 = 50% of sample population will be infected
LD50 = 50% of sample population will die
Pathogen adherence to a host cell requires…?
- receptor: specific carbohydrate or peptide residues on host cell
- adhesin: macromolecule on pathogen to interact with receptor
Define invasiveness. What are the 2 types of infections when it comes to invasiveness?
Ability to invade/spread, penetrating host’s defenses.
1. surface: fail to spread to deeper structures, stays at barrier. uses innate immune system.
2. systemic: spreads systematically via blood/lymph. uses adaptive immune system.
Staph. aureus uses hyaluronidase and lipases as enzymes. What do they do?
Hyaluronidase: Breaks up connective tissues to penetrate deep into tissue.
Lipases: Penetrate oily sebaceous glands.
List characteristics of exotoxins.
Typically polypeptides released into surrounding areas. They are antigenic, specific to a bacterial strain. Can be modified to form a toxoid (antigenic but not toxic, sued in immunizations).
What do the following exotoxins cause?
1. cholera toxin
2. diphtheria toxin
3. tetanus toxin
- diarrhea
- cell death by no protein synthesis by ribosomes
- muscle spasms
Where are endotoxins found? Can they be made into a toxoid?
Typically found on outer membrane of gram-negative bacteria, usually LPS (lipid A = toxic). Non-specific.
Cannot be made into a toxoid.
How can microbes avoid the following 3 immune defenses?
1. innate immune defenses
2. adaptive immune defenses
3. drugs
- evade mechanical barriers/phagocytosis
- concealment/changing of antigens, suppress immune response
- antibiotic resistance
