Session 9 - Chronic Health and Infections

Question 1

Why are some infections typical of certain chronic conditions?

Answer 1

• Chronic diseases cause a change in the structure or function of affected tissue
• Can change the interaction between the patient and MOs.
• New interaction with MOs can change the chronic disease, which further affects tissues etc.

Question 2

How can chronic diseases be acquired?

Answer 2

Can be congenital or acquired.

Acquired follow the mnemonic VITAMINN DEI:

Vascular

Infective

Trauma

Autoimmune

Metabolic

Inflammatory

Neurological

Neoplastic

Degenerative

Environmental

Idiopathic

Question 3

What is the inheritance pattern of CF?

Answer 3

Autosomal recessive

Question 4

What deletion happens in CF and what is the result?

Answer 4

Most frequent is DeltaF508 (deletion of phenylalanine at position 508) in CFTR gene which codes for chloride ion channel

Results in viscous mucus in the lungs which blocks ducts and allows pathogens to attach to and colonise.

Question 5

Why is a pseudomonas aeruginosa infection in CF patients difficult to treat?

Answer 5

• CF patients infected by a version that produces mucus
• Mucus forms a biofilm surrounding the aeruginosa, preventing phagocytosis by lung macrophages and antibiotics entering.

Question 6

What organisms infect CF patients?

Answer 6

H influenza –> Staph aureus –> pseudomonas aeruginosa or burkholderia cepacia –> atypical mycobacteria

Question 7

What is COPD?

Answer 7

• Chronic inflammatory response to inhaled irritants, primarily mediated by neutrophils and macrophages.
• Results in breakdown of lung tissue (emphysema) and small airways disease (obstructive bronchiolitis) and increased mucus production.

Question 8

Name 2 bacteria that infect COPD patients

Answer 8

S pneumoniae, ps aeruginosa

Question 9

Name 2 viruses that infect COPD patients

Answer 9

RSV, influenza A

Question 10

Why does Diabetes mellitus cause an increased risk of infection?

Answer 10

• Hyperglycaemia and acidemia in DM impair humoral immunity as well as granulocytes (3 types – basophils, eosinophils and neutrophils) and lymphocyte functions.
• Micro and macrovascular disease results in poor tissue perfusion and an increased risk of infection.
• Diabetic neurpathy causes diminished sensation resulting in unnoticed skin, combined with poorer healing.

Question 11

What ENT infections are DM patients susceptible to?

Answer 11

Malignant or necrotizing otitis externa:

o Infection of pinna of ear by pseudomonas aeruginosa.

o Spreads to adjacent soft tissue, cartilage, and bone.

o Patients present with severe ear pain and otorrhoea (discharge of pus from the ear)

Rhinocerebral mucormycosis:

o Mould fungi which infects those with poorly controlled diabetes, esp. those with diabetic ketoacidosis.

o Fungi colonises the nose and paranasal sinuses, spreading to adjacent tissues by invading blood vessels and causing soft tissue necrosis and bone erosion.

Question 12

Why are DM patients more susceptible to UTIs?

Answer 12

• Diabetic neuropathy leads to defects in bladder emptying. Inability to completely flush urine allows bacteria to invade and multiply.
• Increased risk of asymptomatic bacteriuria and pyuria (urine containing pus), cystitis (inflammation of bladder), and upper RTI.
• Colonisation by enterobacteriaceae e.g. E. coli. Ps aeruginosa.
• This is not specific to diabetes and can occur in any neurological disorder that affects bladder control e.g. alzheimers, cerebral palsy, MS, parkinsons, stroke, or any acquired nerve system damage.

Question 13

Why are DM patients more susceptible to skin and soft tissue infection?

Answer 13

• Sensory neuropathy, atherosclerotic vascular disease, and hyperglycaemia all predispose to an increased risk of skin and soft tissue infection
• Can be caused by staph aureus, beta-haemolytic strep, or polymicrobial causes including previously named bacteria as well as anaerobes.