14 Infection in the immunocompromised host

Question 1

Explain how neutrophils may have qualitative defects.

Answer 1

Chemotaxis - rare, inadequate signalling/receptors/movement

Killing - CGD - no NADPH oxidase, no hydrogen peroxide. Staph aureus risk.

Question 2

What might cause a quantitative lack of neutrophils?

Answer 2

Cancer rx.
Bone marrow malignancy.
Aplastic anaemia caused by drugs.

Question 3

Which infections are neutropenic patients especially at risk of? (5).

Answer 3

E. coli (G-ve bacilli).
S. aureus (G+ve cocci).
Coagulase -ve staph.
Candida spp.
Aspergillus spp.

Question 4

What is the treatment for an infection in a neutropenic patient? (2,2,1)

Answer 4

Aminoglycoside and an antipseudomonal penicillin.
2nd line - carbapenem, antifungals.
GCSF.

Question 5

Which drugs may cause T cell deficiencies? (2).

Answer 5

Ciclosporin (transplantation).

Steroids.

Question 6

Which bacterial, viral (3) and fungal (2) infections are T cell deficient patients most susceptible to?

Answer 6

Listeria monocytogenes.
Mycobacteria.
HSV, CMV, VZV.
Candida spp, ctyptococcus spp.

Question 7

Which protozoan and parasitic infections are T cell deficient patients most at risk of? (3)

Answer 7

Cryptosporidium pavum (faecal-oral, symptomatic rx only).
Toxoplasma gondii (cat, or heart with bradyzoites - asymptomatic).
Strongyloides stercoralis.

Question 8

Three causes of acquired hypogammaglobulinaemias and three commonly resulting infections.

Answer 8

Multiple myeloma, CLL, burns.
Usually encapsulated bacteria:
S. pneumoniae, Giardia lambia, Cryptosporidium.

Question 9

Which infections occur with a complement deficiency? (3)

Answer 9

Encapsulated bacteria
S. pneumoniae - poor opsonisation.
If C5-8 Neisseria meningitides.

Question 10

What does the spleen do? (2)

Answer 10

Source of complement and B cells, removes opsonised bacteria.

Question 11

Which infections are people who take biological therapies at risk of? (4).

Answer 11

Tuberculosis.
Herpes zoster.
Legionella pneumophila.
Listeria monocytogenes.

Question 12

What are the five stages of different infections that can follow organ transplantation?
Which infections occur? (1,2,2,2,2)

Answer 12

Initial disease: Hep B.
Surgery related: ventilator acquired pneumonia, S. aureus.
Organ: Toxoplasmosis, CMV.
Initial opportunistic: CMV, Aspergillus.
Later opportunistic: VZV, Listeria.

Question 13

Which prophylactic antimicrobials are used in immunocompromised patients? (4).

Answer 13

Penicillin.
Cotrimoxazole.
Acyclovir.
Passive immunoglobulin.

Question 14

When should Strongyloides stercoralis be suspected? (3).

Answer 14

Eosinophilia.
G-ve septicaemia.
Tropical/ old POW.

Question 15

Which infections commonly occur after a splenectomy? (4).

Answer 15

Streptococcus penumoniae.
Haemophilis influenza type B.
N meningitides.
Malaria.