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Foundations of Medicine > Pathogens and Hosts > Flashcards

Pathogens and Hosts Flashcards

1
Q

What characterises a clinical infection?

A
  • Inflammation
  • Pain
  • Pyrexia
  • Tachycardia
  • Rigors
  • Increased white cell count
  • Increased C reactive protein (CRP)
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2
Q

What is a pathogen?

A

An organism which can cause disease

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3
Q

What is a commensal?

A

An organism which is part of normal flora e.g E.coil in the gut, Staph aureus in the nose

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4
Q

Define pathogenicity

A

The capacity of a micro-organism to cause an infection

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5
Q

What are the requirements of pathogenicity?

A

Infectivity
Virulence

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6
Q

Define infectivity

A

Ability to become established on or within a host

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7
Q

Define virulence

A

Capacity to cause harmful effects (disease) once established.

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8
Q

What is virulence conferred by?

A

Conferred by virulence factors.

  • Genetically determined microbial components
  • Invasiveness
  • Toxin production
  • Evasion of immune system
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9
Q

What is virulence specific to?

A

Strains, not species

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10
Q

What are exotoxins?

A

A toxin secreted by bacteria

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11
Q

How are exotoxins released?

A

Exotoxins are released extracellularly by the micro-organisim

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12
Q

What are endotoxins?

A

The main component of the outer membrane of the cell wall of Gram-negative bacteria.

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13
Q

What do enterotoxins act on?

A

Enterotoxins are exotoxins which act on the GI tract

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14
Q

Define colonisation

A

The presence of bacteria on a body surface(like on the skin, mouth, intestines or airway) without causing disease in the person.

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15
Q

Define latent (aka asymptomatic) infection

A

An infection that usuallydoes not cause symptomsand can last a long period of time before becoming active and causing symptoms.

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16
Q

When does an infection occur?

A

When a microorganism enters a person’s body and causes harm.

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17
Q

What are the mechanisms of the innate immune system?

A

Physical
Physiological
Chemical
Biological

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18
Q

What are examples of physical barriers of the innate immune system?

A

Skin - Tears, urine, saliva, bile, pancreatic secretions, mucus and sebaceous secretions

Mucous membranes of respiratory, gastrointestinal and urinary tracts

19
Q

What is the role of bronchial cilia?

A

Move microbes and debris up and out of the airways.

20
Q

What are examples of physiological barriers?

A

Diarrhoea
Vomiting
Coughing
Sneezing

21
Q

How does low pH act as a chemical barrier to pathogens?

A

The relativelylow pH in certain parts of the body prevents pathogen growth.

22
Q

What are examples of structures with low pH?

A

Skin–pH 5.5
Gastricacid–pH 1-3
Vagina–pH 4.4

23
Q

What is the main biological barrier to pathogens?

A

Normal flora found in the body

24
Q

Where can body flora be found?

A

Nasopharynx

Mouthand throat

Skin

GI tract

Vagina

25
Q

What are the mechanisms of the adaptive immune system?

A

Cell mediated immunity
Humoral immuity

26
Q

What is cell mediated immunity mediated by?

A

T lymphocytes against intracellular pathogens

27
Q

What is humoral immunity mediated by?

A

Antibodies

28
Q

Discuss cell mediated immunity

A

An immune response that does not involve antibodies.

Rather, phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen.

29
Q

What is humoral immunity based on?

A

Serum antibodies that are produced by plasma cells and bind to antigens in order to assist with their elimination.

30
Q

What is cell mediated immunity based on?

A

The action of cytotoxic cells that activate other immune cells andhelp eliminate pathogens and infected host cells.

31
Q

What is humoral immunity also known as?

A

Antibody-mediated immunity.

With assistance from helper T cells, B cells will differentiate into plasma B cells that can produce antibodies against a specific antigen.

32
Q

What does the humoral immune system deal with?

A

Antigens from pathogens that are freely circulating, or outside the infected cells.

33
Q

What are common sites of viral entry?

A

Mucosal linings of the respiratory, alimentary, and urogenital tracts

The outer surface of the eye

The skin

34
Q

What is antigenic drift?

A

Minor changes (natural mutations) in the genes of flu viruses occurs gradually over time to generate antigenic variants

35
Q

What is antigenic shift?

A

Abrupt major changes in virus antigenic structure due to combination of different strains from different hosts

36
Q

What does influenza A virus infect?

A

Cells of respiratory system

Destruction of respiratory epithelium - secondary bacterial infections

37
Q

What causes fever in influenza A virus?

A

Alterned cytokine expression leading to fever

e.g interleukin-1 and interferon - Avian influenza virus (H5N1) causes cytokine storm

38
Q

What are enteroviruses?

A

Viruses that are:

  • Small
  • Icosahedral shaped
  • Non-envelope

Virons are relatively simple, consisting of a:

Protein capsid surrounding a single-stranded, positive sense RNA genome.

39
Q

What can enterovirus cause?

A
  • Croup (breathing difficulty and harsh cough)
  • Mouth sores.
  • Skin rashes.
  • Sore throat.
  • Chest pain if the infection affects the heart muscle or sac-like covering around the heart (pericarditis)
40
Q

What are examples of enteroviruses?

A
  • Poliovirus
  • Respiratory infections (many enteroviruses)
  • Myocarditis (coxsackie B viruses)
41
Q

What can viruses turn into?

A

When viruses cause an infection, they spread their DNA, affecting healthy cells’ genetic makeup and potentially causing them to turn into cancer.

42
Q

What are the mechanisms in which a virus can turn into cancer?

A
  • Directly damage DNA in host cells, resulting in cancer.
  • Altering the immune system
  • Chronic inflammation.
  • Disrupting the body’s normal regulation of cell division.
43
Q

What can papillomaviruses and HPV infections casue?

A

Cervical carcinoma

44
Q

What can retroviruses cause?

A

Lymphomas and leukemias

Foundations of Medicine (56 decks)

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