define microbe, host, and environment
microbe- able to cause disease
host- susceptible to infection
environment- affect microbial survival + transmission
define pathogenicity + virulence
pathogenicity- ability to cause disease
virulence- degree to which a microbe is pathogenic (is dependent on virulence factors)
define mutualism, commensalism, parasitism, opportunism
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)
4 principles of disease
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)
define communicable, contagious, non-communicable, endogenous infection, and exogenous infection
-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
what are some examples of reservoirs of infection
-humans
- animals
-soil/water
modes of transmission
-physical contact (direct + indrect (droplets))
-airborne
-water borne
-food borne
-vectors
portal of entry + exist
-skin
-respiratory tract
-gastrointestinal tract
-urogenital (STD, UTI)
-transplacental
how do we stop microbes from entering
-decrease reservior of infection
-alter behaviour to alter to block mode of transmission
- barrier protection to prevent portal of entry
infectious disease development
- incubation (no symptoms, microbe attempting to establish infection),
- prodromal illness (mild symptoms, microbe multiplication, host defence may still overcome )
- invasive phase (identifiable disease syndrome, lead to fatal outcome if microbial growth not checked, cell damage occurs)
- decline (decrease in microorganisms due to immune response or medical treatment)
- are 2 possible outcomes
- fulminating phase (symptoms appear suddenly, fatal outcome)
- recovery + convalescence (host defence overcomes, symptoms subside, host repairs damage)
*refer to image 1
signs of infectious disease
-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)
treatmnets for infectious diseases
-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)
signs of infectious disease on skin
- 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)
Define localised, disseminated, systemic infection, and chronic vs persistent infection
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)
