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Infection and Immunity > Week 7 - Infections on Surfaces + Allergy > Flashcards

Week 7 - Infections on Surfaces + Allergy Flashcards

1
Q

What is microbiota?

A
  • The microorganisms that typically inhabit a body organ
  • Micro-organisms carried on skin and mucosal surfaces
  • Normally harmless or even beneficial
  • Transfer to other sites can be harmful
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2
Q

What is the normal microbiota found on the skin?

A
  • Viruses:
    — Papilloma
    — Herpes simplex
  • Bacteria
    — Gram positive
    • Staph aureus
    • Coagulase negative streptococci
    • Corynebacterium
    — Gram negative
    • Enterobacteriaceae
  • Fungi
    — Yeasts
    — Dermatophytes
  • Parasites
    — Mites
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3
Q

How can people get surface infections?

A
  • Invasion
  • – E.g. step pyogenes pharyngitis
  • Migration
  • – E.g. Escherichia coli urinary tract infection
  • Innoculation
  • – E.g. coagulase negative staphylococcus prosthetic joint infection
  • Haematogenous
  • – E.g. viridans strep endocarditis
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4
Q

What are some examples of external natural surface infections?

A
  • Cellulitis
  • Pharyngitis
  • Conjunctivitis
  • Gastroenteritis
  • Urinary tract infection
  • Pneumonia
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5
Q

What are some examples of internal natural surface infections?

A
  • Endovascular
  • – Endocarditis
  • – Vasculitis
  • Septic arthritis
  • Osteomyelitis
  • Empyema
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6
Q

What are some examples of prosthetic surface infections?

A
  • Intravascular lines
  • Peritoneal dialysis catheters
  • Prosthetic joints
    — Causative organisms:
    • Coagulase negative staphylococci
    • Staphylococcus aureus
  • Cardiac valves
    — E.g. prosthetic valve endocarditis
    • Coagulase negative staphylococci
    • Viridans streptococci
    • Enterococcus faecalis
    • Staph aureus
    • HACEK group
    • Candida
  • Pacing wires
    — Endocarditis, causative organisms:
    • Coagulase negative staphylococci
    • Staph aureus
  • Endovascular grafts
  • Ventriculo-peritoneal shunts
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7
Q

Describe the pathogenesis of infections at a surface

A
  • Adherence to host cells or prosthetic surface
  • Biofilm formation
  • Invasion and multiplication
  • Host response
  • – Pyogenic
  • – Granulamatous
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8
Q

How can you identify surface infections?

A
  • Aim is to identify infecting organism and its antimicrobial susceptibilities
  • Challenges:
  • – Adherent organism
  • – Low metabolic state/small colony variants
  • Blood cultures
  • Tissue/prosthetic material sonication and culture
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9
Q

How do you treat surface infections?

A
  • Aim:
  • – Sterilise tissue
  • – Reduce bioburden
  • Antibacterials
  • Remove prosthetic material
  • Surgery – resect infected material
  • Challenges:
  • – Poor antibacterial penetration into biofilm
  • – Low metabolic activity of biofilm microorganism
  • – Dangers/difficulties of surgery
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10
Q

How can you prevent surface infections?

A
  • Natural surface
  • – Maintain surface integrity
  • – Prevent bacterial surface colonisation
  • – Remove colonising bacteria
  • Prosthetic surfaces
  • – Prevent contamination
  • – Inhibit surface colonisation
  • – Remove colonising bacteria
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11
Q

What are the different types of hypersensitivity reactions?

A
  • Type I or immediate (
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12
Q

What is hypersensitivity?

A

The non-specific immune response that are either inappropriate or excessive and that result in harm to the host

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13
Q

What are the common features of hypersensitivity reactions?

A
  • Sensitisation phase
  • – First encounter with the antigen
  • Effector phase
  • – Clinical pathology upon re-exposure to the same antigen
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14
Q

Describe the pathophysiology behind a hypersensitivity reaction

A
  • People are born with the TH2 phenotype
  • – TH2 phenotype leads to allergic reactions
  • Upon appropriate and sufficient immune system exposure, the phenotype can change to TH1, which does not produce allergic reactions
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15
Q

What are some common allergens?

A
  • House dust mite, cockroaches
  • Animals, especially domestic pets such as cats and dogs
  • Tree and grass pollens
  • Insect venom such as that contained in wasp and bee stings
  • Medicines
  • – E.g. penicillin
  • Chemicals
  • – E.g. latex
  • Foods
  • – E.g. peanuts, nuts, milk
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16
Q

Describe the immune mechanism of allergic reaction

A
  • Mast cells are activated by antigen-specific IgE
  • – Mast cells may be in the epidermis, deep dermis or there may be systemic activation
  • This triggers the release of:
  • – Histamine
  • – Chemokines
  • – Leukotrienes
  • – Prostaglandins
  • Leads to:
  • – Increased vascular permeability
  • – Vasodilation
  • – Bronchial constriction
17
Q

What are the signs and symptoms of anaphylaxis?

A
  • Swelling of the conjunctiva
  • Runny nose
  • Swelling of lips, tongue and/or throat
  • Heart and vasculature:
  • – Fast or slow heart rat
  • – Low blood pressure
  • Skin
  • – Hives
  • – Itchiness
  • – Flushing
  • Pelvic pain
  • CNS
  • – Lightheadedness
  • – Loss of consciousness
  • – Confusion
  • – Headache
  • – Anxiety
  • Respiratory
  • – Shortness of breath
  • – Wheezes or stridor
  • – Hoarseness
  • – Pain with swallowing
  • – Cough
  • GI
  • – Crampy abdominal pain
  • – Diarrhoea
  • – Vomiting
  • Loss of bladder control
18
Q

How do you treat an anaphylactic shock?

A

Adrenaline

  • Intramuscular injection
  • Method of action:
  • – Reverses peripheral vasodilation, reduces oedema and alleviates hypotension
  • – Reverses airway obstruction/bronchospasm
  • – Increases the force of myocardial contraction
  • – Inhibits mast cell activation
  • Timesaver vs lifesaver
  • Multiple doses may be required
  • Proper use of epipen is important
  • Do not delay treatment!!
  • Monitor pulse, blood pressure, ECG, oximetry
19
Q

How do you diagnose allergies?

A
  • Clinical history
  • – Atopy
  • – Allergens
  • – Seasonality
  • – Route of exposure
  • Blood tests
  • – Serum allergen-specific IgE
  • – Serum mast cell tryptase, histamine
  • Skin prick tests
  • – Wheal and flare reaction
  • – Can observe a range of allergens
  • Challenge tests
  • – Food and drug allery
  • – Slight risk of anaphylaxis in highly sensitised patients
20
Q

How do you manage allergies?

A
  • Allergen avoidance/elimination
    — Read food labels
    — House dust mite avoidance
    — Avoid high risk situations
  • Education
    — Parents, to recognise symptoms
    — Patients, to use EPIPEN
    — Call emergency services when EPIPEN used
    — Schools and social activities
  • Medic alert information
  • Drugs
    — Antihistamines
    • Alternate sedating/non-sedating forms
    • Corticosteroids
    • Topical or systemic
    • Anti-IgE IgG
    • Anaphylaxis
    • Injectable adrenaline (epipen)
  • Allergen desensitisation
    — Patients with high risk of systemic attacks
    — Involves the administration of increasing does of allergen extracts over a period of years
    • Given to patients by injection or drops/tablets under the tongue

Infection and Immunity (10 decks)

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