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EOS Principles of diseases > bacterial pathogens > Flashcards

bacterial pathogens Flashcards

1
Q

define infection

A

is the growth & multiplication of a microbe in a body with or within disease

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2
Q

define disease

A

disease occurs when infections disrupts the normal functioning of the host

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3
Q

define pathogenicity?

A

is the capacity of a bacteria to cause disease

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4
Q

define virulence?

A

is the measure of the pathogenicity of the microorganism

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5
Q

define pathogenesis

A

refers to both the mechanisms of infection & the mechanism by which disease develops

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6
Q

what determines host susceptibility to bacterial infection?

A
  • determined by host defences & bacterial virulence

- host defences can be compromised by destruction of barriers or defects in the immune response

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7
Q

what are opportunist pathogens?

A
  • are typically members of normal flora & typically cause disease when they are introduced into an unprotected site
  • usually occur in animals with an underlying condition
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8
Q

what are strict pathogens?

A
  • are more virulent than opportunistic pathogens & cause disease in a normal healthy animal
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9
Q

what 5 attributes of a bacteria contribute to disease?

A
  1. access to host
  2. able to adhere & colonise the surface of the host
  3. invasive
  4. able to survive or evade host defence mechanisms
  5. able to produce harm to host tissues
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10
Q

what are the main portal of entry that bacteria use as access to the host?

A

main portals of entry are via the:

  • mucous membranes
  • skin
  • parenteral
  • many microbes have a preferred portal of entry & must entry a specific way & in a certain place to cause disease
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11
Q

how do microbes adhere to a surface of host?

A
  • pathogens have adhesions or ligands that bind specifically to host cell surface receptors
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12
Q

how do bacteria colonise in a host?

A
  • bacteria colonise by reproducing via binary fission

- must survive & reproduce despite hosts defence mechanisms

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13
Q

how are bacteria invasive (penetrate into host cells)?

A
  • bacteria produce invasions which alter the actin filaments of the host cytoskeleton, allowing microbe to enter cell
  • some use active phagocytosis
  • bacteria can use microbial enzymes to invade cell (lyse cells, form or dissolve clots or dissolve materials in tissues)
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14
Q

how can bacteria evade the host immune system?

A
  • interfering with phagocytosis by possessing a non-antigenic capsule
  • interfering with phagocytic killing
  • avoiding antibodies or complement
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15
Q

how can bacteria harm the host

A

bacteria can harm the host by:

  1. direct damage
  2. hypersensitivity reactions
  3. toxins (exotoxins & endotoxins)
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16
Q

how do bacteria harm the host by direct damage?

A
  • by inducing cells to engulf the bacteria cell & once engulfed, its metabolism & multiplication kills the host cell
17
Q

how do bacteria harm the host by hypersensitivity reactions?

A
  • by causing an immune response that is more excessive than normal to a point where it leads to damage or is potentially damaging to the host
18
Q

how do bacteria harm the host by toxin production?

A
  • toxins are poisonous substances produced by microbes
19
Q

define toxigenicity?

A
  • is the ability of a microbe to produce toxins
20
Q

define toxaemia

A
  • is the presence of toxins in the blood
21
Q

define toxic effects

A

fever, cardiovascular problems, diarrhoea, shock, destruction of RBCs & blood vessels & nervous system disruption

22
Q

describe exotoxins?

A
  • exotoxins are produced inside gram-positive bacteria as a part of their growth & are metabolised & excreted
  • are soluble in body fluids & are rapidly transported throughout the body in blood or lymph
  • responsible for disease symptoms & death
  • antibodies called antitoxins provide immunity against exotoxins
23
Q

define toxoids

A
  • are toxins that have been altered by heat or chemicals & are used as vaccines for diphtheria & tetanus
24
Q

describe endotoxins

A
  • are part of the outer portion of the cell wall of gram negative bacteria
  • endotoxins are present in Lipid A of the outer membrane
  • are released when bacteria die & cell wall breaks apart
  • do not promote the formation of effective antibodies
25
Q

define infectious disease

A
  • an infectious disease occurs when the presence of a living organism in or on the animal induces abnormal function that leads to clinical signs
26
Q

what does a bacteria’s pathogenicity depend on?

A
  • its ability to invade the host, multiply in the host & avoid being damaged by the host’s defences
26
Q

what does a bacteria’s pathogenicity depend on?

A
  • its ability to invade the host, multiply in the host & avoid being damaged by the host’s defences
  • number of infectious organisms entering
  • susceptibility of host
  • virulence of pathogen
27
Q

what are non-pathogens?

A
  • microbes that are not pathogens
  • considered the first line of defence in host defences
  • commensals that become opportunists due to failure of host defences, introduction to an unusual site or disturbance of normal flora
  • secondary infection
28
Q

what is the carrier state?

A
  • an animal is in a carrier state when it harbours a disease organism in its body without clinical signs & acts as carriers of infection
  • may shed disease agent continuously or intermittently
29
Q

what is a dormant/latent infection?

A
  • is an infection that lies dormant in the body for a period of time but may become active under certain circumstances
  • can persist without shedding or shed occasionally
30
Q

what are chronic/persistent infections?

A
  • infections that have been present for a long time or keeps recurring
  • develop after acute infection
31
Q

acute infection vs subacute infection

A

acute infection
- has a short severe clinical course of a few days & invading bacteria are usually cleared from the body by the host’s immune system

subacute infections
- produce clinical effect to a lesser intensity

32
Q

what is septicaemia?

A
  • is the presence of bacteria & toxins in blood
  • caused by invasion of the bloodstream by virulent microbes
  • pathogenic microbes multiply & persist in blood stream to produce systemic disease
33
Q

define bacteraemia?

A
  • temporary presence of bacteria in blood

- bacteria are only present transiently in bloodstream & don’t replicate

EOS Principles of diseases (12 decks)

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