9) Chronic Infections and Allergy

Question 1

How can chronic diseases lead to infection?

Answer 1

Change in the structure or function of affected tissues/organs which change interaction between micro-organisms and patient. Also, altered presence of micro-organisms and the consequences of treatment e.g. with antibiotics and steroids

Question 2

What two main types of chronic diseases can you have?

Answer 2

Congenital and acquired

Question 3

Examples of acquired chronic diseases:

Answer 3

Vascular, infective, traumatic, autoimmune, idiopathic, degenerative

Question 4

Inheritance pattern of cystic fibrosis?

Answer 4

Autosomal recessive

Question 5

What defect underlies cystic fibrosis?

Answer 5

Defect in cystic fibrosis transmembrane conductance regulator gene in exocrine glands

Question 6

What is the most frequent mutation in CF?

Answer 6

Most frequent is F508 (deletion of phenylalanine at position 508)

Question 7

What does CFTR do?

Answer 7

Move Cl- ions into mucus so water follows

Question 8

What is the consequence of the defect in CF?

Answer 8

Mucus becomes dehydrated and thick causing blockage in small ducts

Question 9

What are the consequences of CF on a child?

Answer 9

Reduced growth due to malabsorption (pancreas affected)

Recurrent infections

Question 10

What causes CF sufferers to have increased susceptibility to infection?

Answer 10

In CF lungs have thick and sticky mucus, which provides the perfect environment for bacteria to infect and propagate. Cilia are flattened and the ability to clear bacterial infection reduced

Question 11

What micro-organisms are opportunistic in CF?

Answer 11

H influenza, S Aureus
Pseudomonas aeruginosa, Burkholderia cepacia
Atypical Mycobacteria, Candida albicans, Aspergillus fumigatus

Question 12

Management for CF:

Answer 12

Pancrease (mix of digestive enzymes)
Physiotherapy
Vitamins
Nebulisers and salbutamol

Question 13

What is the classification of Pseudomonas aeruginosa?

Answer 13

Gram negative bacilli

Question 14

How does Pseudomonas aeruginosa cause infection?

Answer 14

Opportunistic
Attachment –> local infection –> dissemination and systemic disease.
Invasive and toxigenic

Question 15

Why is Pseudomonas aeruginosa hard to treat?

Answer 15

Multi-drug resistant, minimal nutritional requirements and can tolerate wide variety of physical conditions

Question 16

How would you treat against Pseudomonas aeruginosa ?

Answer 16

Ciprofloxacin

IV gentamicin

Question 17

What micro-organisms can cause acute-exacerbations in COPD?

Answer 17

S pneumonia, H influenza, Ps aeruginosa

Respiratory syncytial virus, Rhinovirus

Question 18

What do hyperglycemia and acidemia impair?

Answer 18

Humoral immunity and polymorphonuclear leukocyte and lymphocyte functions

Question 19

In what ways can diabetes increase risk of infection?

Answer 19

Vascular disease causes poor perfusion

Neuropathy causes diminished sensation so unnoticed skin

Question 20

What is malignant otitis externa and what causes it?

Answer 20

Infection of pinna caused by Pseudomonas aeruginosa

Question 21

What is rhinocerebral mucormycosis and what causes it?

Answer 21

Mould infection of sinuses which can cause bony erosion

Question 22

Why are UTIs common with diabetes?

Answer 22

Neurogenic bladder due to diabetic neuropathy leads to defects in bladder emptying, so residual urine

Question 23

What micro-organisms can cause UTIs?

Answer 23

Enterobacteriaceae (e.g. E coli), Ps aeruginosa

Question 24

What bacteria cause skin and soft tissue infection in diabetes?

Answer 24

Staph aureus (folliculitis, cellulitis)
Group A β-haemolytic Streptococcus (cellulitis) – Polymicrobial  (Diabetic foot ulcers and necrotising fasciitis)

Question 25

What infections are those with Down’s syndrome susceptible to?

Answer 25

Respiratory tract infections

Question 26

Why are those with Down’s syndrome susceptible to infection?

Answer 26

Due to true immunodeficiency, altered mucus secretion or the structure of the mouth and airways.

Question 27

What is hypersensitivity?

Answer 27

Antigen-specific immune responses that is inappropriate or excessive and results in harm to host

Question 28

What are the two phases in hypersensitivity?

Answer 28

Sensitization phase: First encounter with the antigen

Effector phase: Clinical pathology upon re-exposure to the same antigen

Question 29

What is the Type I hypersensitivity reaction?

Answer 29

Immediate in response to allergens (which should be harmless), IgE

Question 30

What is the Type II hypersensitivity reaction?

Answer 30

Response to tissue antigens, IgG or IgM (5-12 hours)

Question 31

What is the Type III hypersensitivity reaction?

Answer 31

Response to soluble antigens, IgG or IgM (3-8 hours)

Question 32

What is the Type IV hypersensitivity reaction?

Answer 32

Cell mediated reaction to environmental infectious agents or self antigens (autoimmune)

Question 33

What is the hygiene hypothesis?

Answer 33

Less infection in childhood = more allergies

Question 34

What is atopy?

Answer 34

Genetic tendency to develop allergic diseases

Question 35

What phenotype protects from allergens?

Answer 35

TH1 phenotype

Question 36

What phenotype is less likely to protect from allergens?

Answer 36

TH2 phenotype

Question 37

Name some common allergens:

Answer 37

House dust mite, animals, pollens, insect venom (bee stings), penicillin, latex, foods (milk, egg, nuts, seafood)

Question 38

What is cross reactivity in terms of allergies?

Answer 38

If you are allergic to one thing will be more likely to be allergic to another, often due to similarities in allergens

Question 39

Describe mast cells and where they are located:

Answer 39

Mast cells have large nuclei and many granules. Located in vessels and mucosal tissue.

Question 40

Name some mast cell mediators:

Answer 40

Enzymes - remodel CT
Histamine and heparin - SM contraction and vascular perm
Cytokines and interleukins - inflamm
Chemokines - attraction
Leukotrienes - SM contraction and vascular perm