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
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
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
4
Q
What are some examples of external natural surface infections?
A
- Cellulitis
- Pharyngitis
- Conjunctivitis
- Gastroenteritis
- Urinary tract infection
- Pneumonia
5
Q
What are some examples of internal natural surface infections?
A
- Endovascular
- – Endocarditis
- – Vasculitis
- Septic arthritis
- Osteomyelitis
- Empyema
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
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
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
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
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
11
Q
What are the different types of hypersensitivity reactions?
A
- Type I or immediate (
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
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
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
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
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
