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Infection > Introduction to infection > Flashcards

Introduction to infection Flashcards

1
Q

what is an infection?

A

Invasion of a host tissue by micro-organisms (where they should not be)

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2
Q

disease caused by

A
  • Microbial multiplication
  • Toxins
  • Host response
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3
Q

how do people get infected

A

From a source directly or indirectly

  • from person to person
  • fromt environment
  • from a vector
  • from animals
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4
Q

microbiota

A

“ecological communities of commensal, symbiotic and pathogenic microorganisms” found in and on all multicellular organisms studied to date from plants to animals.

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5
Q

where are microbiota usually found

A

on the skin or mucosal surfaces

*usually harmless and even beneficial*

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6
Q

when can commensal microbiota be harmgul

A

when they are transfered to others sites e.g. Neisseria meningococcal meningitis

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7
Q

Neisseria meningococcal meningitis

A
  • Found in around 1 in 10 people
  • Will very rarely cause disease
  • Cause disease when they go to non-commensal places-Cystitis
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8
Q

how do people get ifnected

A
  1. microbiota
  2. physical contacgt
    • e.g. sexually tranmitted
  3. airborne spread
    • e.g. chickenpox
  4. vectors
    • e.g. mosquito for malaria
  5. through the environment
    • ingestion of contaminated food or water
      • e.g. food borne diarrhoea
      • cholera
  6. inhalation of air contaminated
  7. contact with contaminated usrfaces inc medical devices
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9
Q

modes of transmission can be….

A

horizontal or vertical

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10
Q

horizontal mode of tranmission via

A
  • Contact
  • Inhalation
  • Ingestion
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11
Q

contact can be

A

direct

indirect

vector

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12
Q

inhalation

A

airborne transmission- coughing

  • droplets
  • aerosols
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13
Q

ingestion

A

faecal-oral transmission

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14
Q

vertical transmission

A

Mother to child, before or at birth e.g. HIV

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15
Q

how can micro-organisms be spread in the body?

A

contiguous spread

haematogenous spread

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16
Q

contiguous spread

A
  • infection spreading locally
    e. g. a spot that spreads across the skin
17
Q

Haematogenous spread

A
  • blood borne

Tissue troponism

Viral infections e.g. enterovirus’ invade via the gut

18
Q

virulence factors

A

Virulence factors are molecules produced by bacteria, viruses, fungi, and protozoa that add to their effectiveness and enable them to achieve the following:

  • colonization of a niche in the host (this includes attachment to cells)
  • immunoevasion, evasion of the host’s immune response[1]
  • immunosuppression, inhibition of the host’s immune response
  • entry into and exit out of cells (if the pathogen is an intracellular one)
  • obtain nutrition from the host
19
Q

types of virulence factors

A

exotoxins

endotoxins

20
Q

exotoxins

A

Exotoxins are actively secreted by some bacteria

◦Cytolytic

◦AB toxins

◦Superantigens

◦Enzymes

21
Q

endotoxins

A

Endotoxin is a component (lipopolysaccharide (LPS)) of the cell wall of gram-negative bacteria. It is the lipid A part of this LPS which is toxic. Lipid A is an endotoxin. Endotoxins trigger intense inflammation.

*recongised by cellular defences*

22
Q

micro-organisms can also cause disease due to

A

host response

  • Sometimes direct- will quickly eradicate local infection
  • Can sometimes cause disease e.g. sepsis and meningitis
23
Q

Disease determinants: Pathogen

A

Virulence factors

Inoculum size

Antimicrobials

24
Q

Disease determinants: Patient

A
  • Site of infection
  • Co-morbidities
    • As you get older more likely to have chronic condition
    • E.g. those with diabetes more likely to get infections
25
Q

questions we need to ask when we think someone is infected?

A
  • Is there an infection?
  • Where is the infection?
  • What is the cause of infection?
  • What is the best treatment?
26
Q

taking a history of someone with a potential infection

A

Symptoms

  • focal, systemic ?
  • severity
  • duration

Potential exposures

27
Q

examination of someone with a potential infection

A

organ dysfunction tests

28
Q

investigations of someone with a suspected infection are…

A

specific (blood culture) or supportive (CRP)

29
Q

supportive investigations

A
  • Full blood count- neutrophils, lymphocytes
  • CRP
  • Blood chemistry- liver and kidney function tests
  • Imaging- X-ray, US, MRI
  • Histopathology
30
Q

specific types of bacteriology: M, C &S

A

microscopy

culture

antibiotic susceptibility

31
Q

Virology

A
  • Antigen section (virus)
  • Antibody detection (the patients response)
  • Detecting viral nucleic acid (DNA or RNA)

Infection (36 decks)

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