Theme 2 Lecture 12: Infections in the Immunocompromised Host Flashcards
What is the definition of immunocompromised?
- disruption of specific defence of an organ/system
- can be humoral or cellular
What are congenital infections?
affect unborn foetus or newborn infant.
generally caused by viruses that may be picked up by the baby at any time during pregnancy up through the time of delivery
What are our innate defences?
- skin (bacteria, sebum, normal flora) e.g if burns
- mucous membranes (tears, urine flow, phagocytes)
- lungs (goblet cells, mucocilary escalator) e.g cystic fibrosis
- interferons, complement, lysozyme, acute phase proteins
- normal commensal flora in gut
When might innate defences alter?
at extremes of age, pregnancy, or if patient is malnourished
Burns leave patients susceptible to which infections?
pseudomonas infections
What is our second line of defence after our innate defences?
the neutrophil
What are qualitative neutrophil defects?
rare, congenital,
inadequate signalling and chemotaxis of neutrophils
neutrophils loose ability to kill or chemotaxis so they do not work
What are quantitative neutrophil defects?
less neutrophils, “neutropenic” = more likely to get an infection
e.g cancer treatment, bone marrow malignancy, asplastic anaemia
Is CGD a result of a qualitative or quantitative neutrophil defects?
qualitative
NADPH system dosen’t work so phagocytosis dosen’t work
these patients are at risk of staph aureus infections
What is the treatment for neutropenic patients?
- broad spectrum antibiotics
- e.g antipseudomonal penicillin +/- gentamicin
- 2nd line treatment if 1st line dosen’t work e.g carbapenem
What types of infections are neutropenic patients susceptible too?
- bacterial infections e.g E.coli, S.aureus
- often normal flora e.g coag neg staph
- fungal infections - candida spp, aspergillus spp
- viruses
What are the two types of T cell deficiencies?
- congenital - rare - T helper dysfunction +/- hypogammaglobulinaemia
- acquired e.g drugs, steroids, viruses
What is cryptosporidium parvum?
- oocytes shed by cattle/humans
- transmission through faecal oral route
- more dangerous in patients with T cell deficiencies
- causes cryptosporidiosis - a disease of the intestines
What parasite causes toxoplasmosis?
toxoplasma gondii
What is hypogammaglobuliaemias?
- reduced serum antibody levels
- can be congenital e.g X linked agammaglobulinaemia (rare)
- acquired e.g multiple myeloma, burns
- treatment is immunoglobulins
which parasite has a characterstic smiley face appearance under a microscope and what does it cause?
giardia
causes fatty stool/ diarrhoea
Patients with a complement deficiency are prone to which encapsulated bacterial infections?
neisseria meningitidis
s.pneumoniae
How is the spleen involved in immunology?
it is a source of complement and antibody producing B-cells, removes opsonised bacteria from blood
What do biologics do?
- inhibit inflammatory cytokine signals e.g TNF inhibiting T-cell activation, or depleting B cells e.g used in severe rheumatoid arthritis
- risk of tuberculosis, herpes zoster, legionella pneumophila and listeria monocytogenes
What are the 2 types of organ transplantation?
- solid organ transplants
2. stem cells in haematological malignancy
What does anti-rejection treatment do?
- suppresses cell mediated immunity to stop effects of cytotoxic and natural killer cells
- degree of immunosuppression varies on how closely the donor and recipient are matched and organ involved
How can we investigate infections in immunocompromised patients?
- history and exam
- urgent diagnosis and treatment
- blood cultures
- respiratory samples
- urine, serology samples, antibody/antigen
- radiology and histopathology
