Wk 1

Question 1

define microbe, host, and environment

Answer 1

microbe- able to cause disease
host- susceptible to infection
environment- affect microbial survival + transmission

Question 2

define pathogenicity + virulence

Answer 2

pathogenicity- ability to cause disease

virulence- degree to which a microbe is pathogenic (is dependent on virulence factors)

Question 3

define mutualism, commensalism, parasitism, opportunism

Answer 3

mutualism- 2 independent organs living together with mutual benefit (maintains acid pH + protection post puberty)

commensalism- 1 benefits, other neutral (resides on skin, can tolerate high salt conc.)

parasitism- 1 organism benefited, other harmed as result (pathogenic microbes)

opportunism- 1 benefits by opportunity (e.g. thrush)

Question 4

4 principles of disease

Answer 4

able to
-gain entry to host (have reservoir of infection, portal of entry + exit, and mode of transmission)
-attach + multiple (microbial pathogenesis, virulence factors, quorum sensing)
-able to evade host defences (physical barrier: skin, innate cellular defenses: phagocytosis, and adaptiv eimmunity: antibodies)
-cause damage to cells + tissues (physical invasion/disruption, toxins, immunopathology)

Question 5

define communicable, contagious, non-communicable, endogenous infection, and exogenous infection

Answer 5

-communicable: 1 host to another
-contagious: degree to which a disease in communicable
-non-communicable: nonhuman/animal spread
endogenous infection: origin of the microbe is self
-exogenous infection: origin from another source

Question 6

what are some examples of reservoirs of infection

Answer 6

-humans
- animals
-soil/water

Question 7

modes of transmission

Answer 7

-physical contact (direct + indrect (droplets))
-airborne
-water borne
-food borne
-vectors

Question 8

portal of entry + exist

Answer 8

-skin
-respiratory tract
-gastrointestinal tract
-urogenital (STD, UTI)
-transplacental

Question 9

how do we stop microbes from entering

Answer 9

-decrease reservior of infection
-alter behaviour to alter to block mode of transmission
- barrier protection to prevent portal of entry

Question 10

infectious disease development

Answer 10

1. incubation (no symptoms, microbe attempting to establish infection),
2. prodromal illness (mild symptoms, microbe multiplication, host defence may still overcome )
3. invasive phase (identifiable disease syndrome, lead to fatal outcome if microbial growth not checked, cell damage occurs)
4. decline (decrease in microorganisms due to immune response or medical treatment)
5. • 6. are 2 possible outcomes
6. fulminating phase (symptoms appear suddenly, fatal outcome)
7. recovery + convalescence (host defence overcomes, symptoms subside, host repairs damage)

*refer to image 1

Question 11

signs of infectious disease

Answer 11

-inflammation
- tissue damage
-vasodilation
-accumulation of phagocytes (release IL-1 to increase temp.)
-increased conc. of white blood cells
-swollen lymph nodes (site of immune responses to infection, produces immune products)

Question 12

treatmnets for infectious diseases

Answer 12

-anti-inflammatory drug (natural process of host defence + healing)
-anti-pyretics ( rise in temp., natural response to promote healing)
-antimicrobial (can change the cause of disease development, release endotoxins resulting in septic shock, indiscriminate use leads to resistance)

Question 13

signs of infectious disease on skin

Answer 13

• lesion
  -erythema (reddened skin, lyme disease)
  -macular rash (adult rubella)
  -abscess (staph. aureus)
• papule (raised red spot)
  -pustule (pus filled lesions)
  -vesicle (small blisters filled with pus, e.g. chicken pox)
  -ulcer (erosion)

Question 14

Define localised, disseminated, systemic infection, and chronic vs persistent infection

Answer 14

Localised- stays in a specific area
-disseminated(able to spread)
-systemic (multi organ affect)
-primary + secondary infection (1st infection predisposes host to another, virus damages mucosa of upper respiratory tract enabling bacteria entry)
-subclinical (no symptoms, immune repsonse triggered)
-latent infection (primary infection established, symptoms subside but microbes not cleared completely, may then reactivate when immunocompromised)
-chronic infection (host remains infectious after symptoms disappear, but becomes a carrier)
-persistent infection (some systemic viral infections + an prion diseases)