Infection 9 Flashcards
What are the congential and acquired causes/categories of chronic disease?
Congenital:
Genetic
Developmental
Acquired:
VITAMIN DE
Vascular
Infective
Traumatic
Autoimmune
Metabolic
Inflammation, Idiopathic
Neurological, Neoplastic
Degenerative
Environmental
How are chronic disease and infection linked?
Chronic disease can predispose to specific infections
Can cause change in structure/function or tissues/organs that alters the patient - microorganism interaction
Micro-organisms and the treatment of infection may further change this interaction
Describe the pathogenesis of Cystic Fibrosis (CF)
Is the primary cause of CF always the same?
Autosomal reccesive disease
Defect in Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene in exocrine glands
Range of different mutations can account for this
Most frequent is Delection of phenylalanine at position 508
What are the consequences of mutation to CFTR?
Defects in Cl- membrane transport
Mucus becomes dehydrated as it lacks osmotic power
Thick mucus blocks the small ducts of exocrine glands
This leads to colonsiation of affected tissues (commonly the lung) with pathological micro-organisms
Lung damage can occur as a result of infection or treatment (Antibiotics/steroids)
Describe the infections a typical patient with CF may experience
Categorises them by when they may occur over the life of a CF patient
Early life onwards:
H. infuenzae
1-2 years:
Staph aureus
2+ years:
Pseudomonas aeruginosa (Common, life threatening, Hallmark of older CF patient)
Burkholderia cepacia (uncommon)
Older teens, Early 20s:
Atypical Mycobacteria
Candida albicans
Aspergillus fumigatus
Why does Pseudomonas aeruginosa limit O2 diffusion into lung tissue in a CF patient?
CF patients commonly infected with mucoid type Pseudomonas aeruginosa that produces excessive biofilm
Psudomonas a, while capable of surviving in aerobic environments thrives in low O2 or anaerobic conditions, thick mucopolysaccharade biofilms are produced to allow this and limit O2 diffusion
Hence O2 diffusion into lung tissue covered by this biofilm is limited
Why is CF such a common disease?
1 in 25 Europeans is a heterozygote (CF carrier)
Lower carrier prevalence in other population, particularly in european countries?
Give examples of bacterial and viral infections that COPD predisposes to
Bacterial:
H. infuenzae
Ps. aeruginosa
Viral:
RSV
Rhinovirus
How does diabetes predispose to soft tissue and skin infection?
Hyperglycaemia and acidaemia impair:
Humoral immunity
Granulocyte (neutrophil, bosaphil and eosinophil) and lymphocyte functions
Diabetic microvascular (atherscelerotic) and macrovascular damage:
Reduces tissue perfusion in periphery
Diabetic neuropathy:
Diminished sensation results in unnoticed skin where infection can take hold in cuts/sores
What are some of the causative organisms of diabetic soft tissue and skin infections?
What infections might each cause?
Staph aureus:
Folliculitis
Cellulitis
Group A Beta-haemolytic strep.:
Cellulitis
Enterobacteriacae and various anaerobes:
Necrotising fasciitis and foot ulcers
What are the 2 common ENT infections in diabetic patients
Describe the spread of infection and name the causative organism(s)
Necrotising otitis externa:
Ps. aeruginosa
Infection starts in external auditory meatus, spreads to adjacent soft tissue, cartilage and bone
Patients present with severe ear pain and ottorrhoea
Rhinocerebral mucormycosis:
Commonly seen in patients with poorly controlled diabetes, especially in diabetic ketoacidosis
Infection colonises nose and parnasal sinuses, spreads to adjacent tissue invading blood vessels and causing soft tissue necrosis and bony erosion
How does diabetes affect bladder control and increase risk of infection?
What infections may occur and what are the causative organisms?
Neurogenic bladder due to diabetic neuropathy leads to defects with emptying
Infections:
Asymptomatic bacteriuria
Pyuria
Cystitis
Upper urinary tract infections
Causative organisms:
Enterobacteriacae (E.g. E. coli), Ps. aeruginosa
Describe the relationship between Down’s syndrome and infection
Otherwise healthy people with Down’s will probably not suffer a great deal more infections than siblings however:
Slight increased risk of resp infections (viral and bacterial) in young people with Down’s
Unknown cause, may be:
Immunodeficiency due to altered humoral and cellular immunity in Down’s
Altered structure of airways/mouth
Altered mucus secretions
