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Infectious Colloquium > Infection, macroorganism defence and first epizootiological factor > Flashcards

Infection, macroorganism defence and first epizootiological factor Flashcards

1
Q

what is infection

A

active or passive invasion, colonisation and replication of a pathogen in human, animal or plant

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2
Q

what is an infectious disease

A

disease resulting from infection
infection in which infected macro organism organ function or health in general is impaired

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3
Q

infectivity

A

ability of pathogen to invade, recognise cell receptors multiply and spread inside of a host

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4
Q

communicable disease

A

an infectious disease transmitted from one individual to another, either by direct contact or indirectly by vectors or fomites

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5
Q

contagious disease

A

communicable disease transmitted by direct contact
infectious disease when it is easily transmitted by contact with an ill animal or their secretions (eg influenza)

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6
Q

conditions in which infections take place

A

natural or experimental

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7
Q

extent of infection

A

general or focal

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8
Q

mono infection

A

infection with a single kind of organism

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9
Q

mixed/polyinfection

A

infection of an organ or tissue by more than 1 micro-organism

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10
Q

primary infection

A

primary pathogens cause disease as a result of their presence or activity within the normal, healthy host.

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11
Q

secondary infection

A

infection by a micro-organism following an infection by another microorganism (primary infection)

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12
Q

opportunistic infection

A

opportunistic pathogens can cause an infectious disease in a host with depressed resistance or if they have unusual access to inside of the body

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13
Q

recurrent infection

A

too great in number, too severe or too long lasting

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14
Q

reinfection

A

an additional infection, with the same micro-organism, occurring after the first infection has resolved

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15
Q

relapse

A

a second episode of a disease due to reemergence of original infection

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16
Q

superinfection

A

an additional infection, with the same microorganism, occurring during the course of an existing infection

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17
Q

exogenous microbes

A

organisms fom outside the body

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18
Q

endogenous microbes

A

organisms from inside the body

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19
Q

auto infection

A

infection with bacteria or virus that persist on or in the body (saprophytes)

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20
Q

nosocomial

A

infection acquired in a health care facility, during a hospital stay

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21
Q

iatrogenic infection

A

infection after medical or surgical management, whether or not the patient was hospitalised

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22
Q

subclinical infection

A

infection that is nearly or completely asymptomatic

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23
Q

latent infection

A

an infection that is inactive or dormant

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24
Q

parasitic infection

A

one benefits at the extent of another

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25
Q

commensalism

A

one benefits but causes no harm

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26
Q

symbiotic infection

A

both benefit - eg gut microflora

27
Q

balanced pathogenicity

A

microorganism causes smallest amount of damage compatible with the need to enter, multiply and be discharged from the body

28
Q

why are some infections still lethal?

A

virulent variants emerged
not enough time to adapt
introduction to new population
host is irrelevant to survival

29
Q

stages of infection

A

exposure (contact)
adhesion (colonisation)
invasion
multiplication
exit

30
Q

portal of entry

A

anatomic site through which pathogens can pass in to host tissue

31
Q

most vulnerable portals of entry

A

GI and respiratory tracts

32
Q

adhesion

A

capability of pathogenic microbes to attach to cells of the body using adhesion factors. different pathogens use various mechanisms to adhere to cells

33
Q

what do microbes attach to cells with

A

protein or carbs called adhesions are found on fimbriae and flagella of bacteria and capsid or membranes of viruses. they bind to specific glycoprotein receptors

34
Q

invasion

A

dissemination of a pathogen throughout local tissues or body

35
Q

what helps invasion

A

exoenzymes or toxins = virulence factors that allow them to colonise and damage host tissues as they spread deeper in to the body

36
Q

how do intracellular pathogens invade

A

enter host cells and reproduce

37
Q

portal of exit

A

a way for pathogen to transmit to new host in order to persist

38
Q

Kochs postulates

A

1 - suspected causative agent must be absent from all healthy organisms but present in all diseased organisms
2 - the causative agent must be isolated from the diseased organism and grown in pure culture
3 - the cultured agent must cause the same disease when inoculated in to a heathy susceptible organism
4 - the same causative agent must then be reisolated from the inoculated diseased organism

39
Q

kochs postulates are wrong because

A
  • assume that pathogen are only found in diseased, not healthy individuals (doesn’t consider asymptomatic)
  • 1 pathogen can cause several disease conditions and 1 disease condition can be caused by several different microorganisms
  • not all healthy test subjects are equally susceptible to disease
  • all pathogens can be grown in pure culture and that animals are reliable models for human disease
40
Q

molecular kochs postulates

A
  1. phenotype of disease should be associated only with pathogenic strains of a species
  2. inactivation of suspected genes associated with pathogenicity should result in a measurable loss of pathogenicity
  3. reversion of the inactive genes should restore the disease phenotype
41
Q

vogralink chain

A

virulence and infective dose
source of infection
mode of transmission
portal of entry
host susceptibility

42
Q

pathogenicity

A

the ability of an organism to cause disease

43
Q

virulence

A

the degree of pathogenicity caused by the organism

44
Q

virulence influence by

A

dose, route of infection, species, age, gender, susceptibility of host and environmental factors

45
Q

pathogenicity v virulence

A

pathogenicity for a given host and pathogen is absolute
virulence is variable
pathogenicity is all or none - it is either pathogenic or not
pathogenicity is applied to groups or species whereas virulence is intended for within group or species comparisons

46
Q

virulence can be measured by

A

mean time to death
mean time to appearance of symptoms
measurement of fever, weight loss etc
measurement of pathological lesions etc

47
Q

important indicators of virulence

A

measured using controlled experiments with lab animals
median infective dose
median lethal dose

48
Q

virulence factors are

A

properties (gene products) that enable a microorganism to establish itself on or within a host of a particular species and enhance its potential to cause disease

49
Q

virulence factors help to

A

invade the hots
evade the host defences
multiply
exit
cause disease

50
Q

bacterial virulence factors

A
  1. adherence components - colonise mucosal sites by using pili to adhere to cells
  2. capsules - protect from opsonization and phagocytosis
  3. invasion enzymes - exoenzymes all them to invade cells and deeper tissues
  4. toxins - exo or endotoxins
51
Q

toxigenicity

A

ability of pathogen to produce toxins

52
Q

examples of exoenzymes

A

hyaluronidase breaks down polysaccharide that glues host cells together
collagenase
fibrinolytic enzymes (streptokinase) destroys fibrin of blood clots so they escape
coagulase promotes blood clotting - protection
nucleases, lipases etc

53
Q

exotoxins

A

small toxins that are released in to cell surroundings (extracellular toxins)
produced by bacteria during infection or directly ingested eg contaminated food

54
Q

3 types of exotoxins

A

cytolytic
superantigens
A-B toxins

55
Q

cytolytic toxins

A

lead to cell lysis
affect cell membrane by forming pores or disrupting the phospholipid bilayer
hemolysins
lecithinase and phospholipase - degrade phospholipids
leukocidins - kill WBC

56
Q

superantigens

A

exotoxins that trigger an excessive, non specific stimulation of immune cells to secrete cytokines.
for example the toxic shock syndrome toxin from S.aureus

57
Q

A-B toxins

A

2 components (initially linked together). one binds to the host receptor, the other enters and damages the cell
Diphtheria toxin
Tetanus toxin
Botulinum toxin

58
Q

cholera toxin

A

cholera B fragment activates adenylate cyclase, increasing the concentration of cAMP and stimulating the secretion of Na and HCO3 - leads to massive water loss through diarrhoea which can be fatal

59
Q

tetanus toxin

A

binds to motor neurons, blocks glycine-stimulated relaxation and leads to spastic paralysis

60
Q

botulinum toxin

A

most toxic substance known - found in improperly canned food
binds to presynaptic motor neurons, prevents release of acetylcholine and leads to flaccid paralysis

61
Q

endotoxins

A

lipopolysaccharide found on the outer membrane of gram negative bacteria
released when cell dies or when bacteria undergo binary fission
lipid component (lipid A) is responsible for toxic properties
lipid A triggers the immune systems inflammatory response
they are not destroyed by heat

62
Q

viral virulence factors

A

1 - viral replication
2 - invasivenes ( adhesion)
3 - tropism
4 - modify the host defuse mechanism

63
Q

how do viruses modify host defence mechanism

A

virokines - not required for viral replication but influence viral pathogenesis by inhibiting the body’s immune response
enable virus to spread in host
intrinsic cell killing effects

64
Q

types of virokines

A

inhibitors of T cel cytotoxicity
inhibitors of cytokine s
inhibitors of complement system
inhibitors of antibody mediated cytolysis
cytokine mimics

Infectious Colloquium (17 decks)

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