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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
commensalism
one benefits but causes no harm
26
symbiotic infection
both benefit - eg gut microflora
27
balanced pathogenicity
microorganism causes smallest amount of damage compatible with the need to enter, multiply and be discharged from the body
28
why are some infections still lethal?
virulent variants emerged not enough time to adapt introduction to new population host is irrelevant to survival
29
stages of infection
exposure (contact) adhesion (colonisation) invasion multiplication exit
30
portal of entry
anatomic site through which pathogens can pass in to host tissue
31
most vulnerable portals of entry
GI and respiratory tracts
32
adhesion
capability of pathogenic microbes to attach to cells of the body using adhesion factors. different pathogens use various mechanisms to adhere to cells
33
what do microbes attach to cells with
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
invasion
dissemination of a pathogen throughout local tissues or body
35
what helps invasion
exoenzymes or toxins = virulence factors that allow them to colonise and damage host tissues as they spread deeper in to the body
36
how do intracellular pathogens invade
enter host cells and reproduce
37
portal of exit
a way for pathogen to transmit to new host in order to persist
38
Kochs postulates
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
kochs postulates are wrong because
- 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
molecular kochs postulates
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
vogralink chain
virulence and infective dose source of infection mode of transmission portal of entry host susceptibility
42
pathogenicity
the ability of an organism to cause disease
43
virulence
the degree of pathogenicity caused by the organism
44
virulence influence by
dose, route of infection, species, age, gender, susceptibility of host and environmental factors
45
pathogenicity v virulence
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
virulence can be measured by
mean time to death mean time to appearance of symptoms measurement of fever, weight loss etc measurement of pathological lesions etc
47
important indicators of virulence
measured using controlled experiments with lab animals median infective dose median lethal dose
48
virulence factors are
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
virulence factors help to
invade the hots evade the host defences multiply exit cause disease
50
bacterial virulence factors
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
toxigenicity
ability of pathogen to produce toxins
52
examples of exoenzymes
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
exotoxins
small toxins that are released in to cell surroundings (extracellular toxins) produced by bacteria during infection or directly ingested eg contaminated food
54
3 types of exotoxins
cytolytic superantigens A-B toxins
55
cytolytic toxins
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
superantigens
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
A-B toxins
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
cholera toxin
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
tetanus toxin
binds to motor neurons, blocks glycine-stimulated relaxation and leads to spastic paralysis
60
botulinum toxin
most toxic substance known - found in improperly canned food binds to presynaptic motor neurons, prevents release of acetylcholine and leads to flaccid paralysis
61
endotoxins
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
viral virulence factors
1 - viral replication 2 - invasivenes ( adhesion) 3 - tropism 4 - modify the host defuse mechanism
63
how do viruses modify host defence mechanism
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
types of virokines
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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