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Infection. > 1.1 - Introduction To Infection > Flashcards

1.1 - Introduction To Infection Flashcards

1
Q

What is an infection

A
  1. Invasion of a hosts tissues by microorganisms

2. These microorganisms cause disease by multiplying, releasing toxins and initiating a host response.

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2
Q

How do people get infections?

A
  1. Microbiota = carried on skin and mucosal surfaces, normally harmless/ beneficial, but become harmful when transferred to other sites. Example is UTI.
  2. Contact and intermediary transmission - Physical contact with people (STI’s), fomites, Airbourne spread/inhalation of air contaminated by organisms (chickenpox), vectors (mosquito for malaria)
  3. Ingestion of contaminated food or water - food bourne diarrhoea
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3
Q

Describe the modes of horizontal and vertical transmission

A

Horizontal = across generations

  • contact (direct, indirect, vectors, fomites)
  • inhalation (droplets, aerosols)
  • ingestion (faecal-oral transmission)

Vertical Transmission = down generation
- mother to child, before or at birth. May be postpartum through breast milk.

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4
Q

How do microorganisms cause disease?

A
  1. Exposure
  2. Adherence
  3. Invasion
  4. Multiplication
  5. Dissemination
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5
Q

How do microorganisms cause host cellular damage?

A
  1. Directly - by toxins damaging host cells (virulence factors)
  2. Consequent to host immune cells (inappropriate host response stimulated by microorganism, gram -ve bacteria)
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6
Q

What are disease determinants?

A

The pathogen

  • virulence factors (exotoxins and endotoxins)
  • inoculum size ( amount of microorganisms around)
  • antimicrobial resistance

Patient

  • site of infection (where does it occur)
  • co-morbidities (patient is more susceptible if they have an existing LTC)
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7
Q

How do we know if a patient has an infection?

A

Asking history

  • symptoms = focal/systemic, severity, duration
  • examination = organ dysfunctions
  • investigation
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8
Q

What is dissemination?

A

The action of spreading by a microorganism. Occurs after multiplication.

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9
Q

What is contiguous spread?

A

Spreading locally in tissue from neighbouring cells.

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10
Q

What is haematogenous spread?

A

Microorganism spreading through blood stream. Widespread infection

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11
Q

What are virulence factors?

A

Virulence factors help increase the survival rates of the microorganism. May by exotoxins or endotoxins

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12
Q

What are exotoxins?

A

a potent toxin formed and excreted by the bacterial cell and found free in the surrounding medium. Break down host cells to release nutrients.
Examples are cytolytic toxins, AB toxins, superantigens, enzymes

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13
Q

What are endotoxins?

A

a toxin associated with the outer membranes of certain gram-negative bacteria, including Neisseria species. Endotoxins are not secreted but are released only when the cells are disrupted; they are less potent and less specific than the exotoxins

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14
Q

How do microorganism harm cells?

A
  1. Directly through exotoxins

2. Consequent to host immune response.

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15
Q

What is the difference between supportive and specific investigations?

A

Specific investigations identify micro-organisms

Supportive investigations support the diagnosis of infections but do not determine the causative microorganism alone.

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16
Q

Give examples of supportive investigations

A

Full blood count - neutrophils/lymphocytes
C-reactive protein (CRP)
Blood chemistry - liver and kidney function tests
Imaging - x-ray, ultrasound, MRI
Histopathology

17
Q

What specific investigations can be done for a bacterial infection?

A

Specimen collected (swabs/fluids/tissues)
M,C&S (microscopy, cultures and susceptibility)
Antigen detection
Nucleic acid detection

18
Q

What specific investigations can be used for a viral infection?

A 
Antigen detection (virus)
Antibody detection (the patients response)
Detecting viral nucleic acid
19
Q

What are common symptoms of infection?

A 
Shivering
Fever
Aches and pain
Sneezing 
Vomiting
Sore throat
20
Q

What barriers do we have to defend against infection?

A

Physical barriers
Physiological barriers
Chemical barriers
Biological barriers

21
Q

what is meant by dissemination?

A

the action or fact of spreading something widely

22
Q

how do we know if a patient has an infection?

A

History - symptoms, severity, duration, potential exposures
examinations - organ dysfunction
investigations - specific, supportive

23
Q

what is Histopathology?

A

Histopathology is the diagnosis and study of diseases of the tissues, and involves examining tissues and/or cells under a microscope.

Infection. (10 decks)

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