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GBE > IAI - pathogenesis of microbial infection > Flashcards

IAI - pathogenesis of microbial infection Flashcards

1
Q

what is symbiosis?

A

the close and often long-term interaction between two different
biological species.

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2
Q

what are the 3 types of symbiotic associations:

A

Commensalism
Mutualism
Parasitism

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3
Q

what is commensalism

A
  • Commensalism: one organism benefits and the other derives neither benefit nor harm
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4
Q

what is mutualism

A
  • Mutualism: association which is beneficial to both organisms involved
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5
Q

what is parasitism

A
  • Parasitism: one organism, the parasite, benefits at the expense of the other.
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6
Q

what is the difference between Obligate intracellular parasites and facultative parasite

A

Obligate intracellular parasitescan only reproduce WITHIN host cells whilst facultative parasites do not rely on its host to continue their life-cycle as can live and reproduce inside AND outside cells

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7
Q

What is the definition of normal flora?

A

population of microorganisms that reside in the skin, mucous membranes and intestinal tract of healthy human body

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8
Q

What are the functions of normal flora?

A
  • Helps development of mucosal immunity.
  • Protects host from colonisation with pathogenic microbes.
  • Aids in digestion of food.
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9
Q

What is the human microbiome?

A

collection of genes of all the microbes in normal flora.

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10
Q

What is the difference between resident and transient flora?

A
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11
Q

What changes in flora occur due to hospitalisation?

A
  • Exogenous environmental infections (e.g. hospital flora found on linen, equipment, water supply)
  • Invasive techniques employed increase risk of infection (e.g. urinary catheters, I.V. lines)
  • Use of antibiotics
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12
Q

Define infection.

A

Infection is the presence of microorganisms in the body

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13
Q

Define colonisation.

A

Colonisation describes when a new microorganism grows on superficial body sites (skin, mucous membranes and GI tract) without invading the body.

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14
Q

Define carrier.

A

A carrier is a person who harbours a microorganism and can be a source of infection for others.

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15
Q

Define pathogen.

A

A pathogen is a microorganism capable of causing disease.

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16
Q

Define microbial pathogenesis.

A

Microbial pathogenesis is the process by which infection leads to disease

17
Q

What is immunopathogenesis?

A

Immunopathogenesis is a primary cause of cell death in many infections is due to killing of infected cells by the host immune system:

  • Cytotoxic T cell mediated attack(e.g. Hepatitis B virus and liver damage)
  • Antibody-mediated damage to the host (e.g. Streptococcus pyogenes and rheumatic fever)
  • Antibody-mediated complement fixation (e.g. Hepatitis C virus exploits the complement system to establish persistence)
18
Q

What are 3 clinical manifestations of disease?

A
  • Symptoms: Subjective features of disease experienced only by the patient. Infections can be asymptomatic (sub-clinical) or symptomatic
  • Sign: Objective manifestations of disease that can be observed and measured by others
  • Syndrome: Group of symptoms and signs characteristic of a disease
19
Q

What are the 4 stages of infectious disease progression?

A
  • Incubation: Time between exposure and onset of a specific clinical sign.
  • Prodrome: Period during which non specific “constitutional” symptoms occur (e.g. fever, malaise, loss of appetite). Not all infectious diseases have a prodromal stage.
  • Illness: Period during which the clinical features of the infection are manifests.
  • Recovery (convalescence): Period during which the illness abates and patient returns to the healthy state.
20
Q

What are the 4 types of infections based on occurrence?

A

Sporadic: the disease occurs only occasionally (e.g. tetanus)

Endemic: the disease is continously present in a population, community or country (e.g. TB and chickenpox)

Epidemic: the disease has greater number of cases than normal in an area within a short period of time i.e. outbreaks occur (e.g. SARS in 2003)

Pandemic: epidemic disease that has worldwide distribution (e.g. flu pandemic in 1918 and 2009)

21
Q

Define outcome (based on infection terms).

A

Outcome – balance between microbial replication and spread and the host’s ability to respond/resist

22
Q

2 types of persistent infections?

A
  • Latent: the microorganism persists after initial clearance, and may have asymptomatic or symptomatic reactivation (e.g. latent tuberculosis, herpes simplex virus and varicella zoster)
  • Chronic: with continued production of the infectious organism and immune evasion (e.g. chronic diabetic foot infection, hepatitis B, HIV). Infected hosts are carriers.
23
Q

What are nosocomial infections?

A

Any infection acquired in a hospital or medical facility. Can affect patients
and health care workers and are common because: (i) are easily moved around by staff,
patients or visitors and (ii) not always can be prevented by proper hand washing.

24
Q

What are 5 determinants of pathogenesis in a host?

A
  • Age (e.g. Infants and elderly are more susceptible to influenza infection)
  • Underlying characteristics that increase susceptibility (e.g. asthma, obesity, diabetes, malnutrition)
  • Genetic variation (e.g. sickle cell trait provides protection to malaria; HIV long-term non- progressors)
  • Immunodeficiency (e.g. opportunistic infections in AIDS patients)
  • Immune response (e.g. “cytokine storm” in influenza infection)
  • Trauma/surgery/foreign body (e.g. surgical implants make it easier for bacteria to cause infection and more difficult to eradicate it)
25
Q

What are iatrogenic infections?

A

Factors that can disrupt the body’s non-specific mechanical barriers to infection make it easier for microorganisms to cause infection, ie:
- Injury associated with therapy
- Plastic and metal “foreign bodies”

26
Q

What are 5 determinants of pathogenesis of an organism?

A
  • Opportunism
  • Attachment
  • Invasiveness
  • Virulence
  • Effects of infection on cells (Cellular Pathogenesis)
27
Q

What is tissue tropism?

A

the specific preference or affinity that a virus or pathogen has for infecting particular types of cells or tissues within a host organism. (e.g. rhinoviruses infect only the respiratory tract).

28
Q

what determines tissue tropism?

A

Attachment is one of several factors that determine tissue tropism as the need for a specific cell receptor narrows the species and the type of cells the pathogen can enter.

29
Q

What is a permissive cell?

A

A permissive cell is one that allows a pathogen to replicate.

30
Q

What is pathogenicity?

A

Pathogenicity is the ability of a microbe to cause disease.

31
Q

What are the 4 bacterial virulence factors?

A
  • Adhesins
  • invasins.
  • Endotoxins: Lipopolysaccharides(LPS) present in the cell wall of Gram-negative bacteria.
  • Exotoxins: Secreted proteins produced by Gram-positive and Gram-negative bacteria .
32
Q

What are superantigens (SAgs)?

A

Superantigens (SAgs) are toxins that stimulate the immune system.

SAgs do not require processing to small peptides. They can bind to MHC-II molecules non-specifically and stimulate a large number of T cells.

33
Q

do keats quiz on pathogenesis of microbial infection

A

https://keats.kcl.ac.uk/mod/lesson/view.php?id=6620871

34
Q

what are 4 types of invasins

A
  • Collagenase and hyaluronidase: Degrade collagen and hyaluronic acid disrupting the epithelial basal lamina and allowing bacteria to spread through subcutaneous tissues (e.g. S. pyogenes)
  • Coagulase: Triggers the formation of a fibrin clot around the bacteria to protect them from phagocytosis (e.g. S. aureus)
  • Leukocidins: Degrade white blood cells (e.g. S. aureus)
  • Hemolysins: Degrade red blood cells (e.g. Streptococci, staphylococci and clostridia )
35
Q

Prodrome is one of the four stages
of disease progression always observed in an infectious disease

true or false

A

FALSE - Not all infectious diseases have a prodromal stage.

36
Q

what is incubation in the 4 stages of infectious disease progression?

A

Time between exposure and onset of a specific clinical sign.

37
Q

what is Prodrome in the 4 stages of infectious disease progression?

A

Period during which non specific “constitutional” symptoms occur (e.g. fever, malaise, loss of appetite). Not all infectious diseases have a prodromal stage.

38
Q

what is Illness in the 4 stages of infectious disease progression?

A
  • Period during which the clinical features of the infection are manifests.
39
Q

what is convalescence in the 4 stages of infectious disease progression?

A

Period during which the illness abates and patient returns to the healthy state.

GBE (58 decks)

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