Infections in the Immunocompromised Flashcards
What leads to someone becoming immunosuppressed?
What tends to cause infections and how can you predict them?
Disruption of specific defence of an organ/system
you can often predict the infection if you know the underlying disease
infections can be caused by organisms of low pathogenicity / opportunistic infections
What are the 2 host defences against infection?
What are the 2 types of infection
- Non-specific innate immune system
- Specific adaptive immune system - humoral or cellular
Infections can be congenital or acquired
What are the innate defences against infection?
Skin:
- barriers
- sebum
- normal flora
Mucous membranes:
- tears
- urine flow
- phagocytes
Lungs:
- goblet cells
- muco-ciliary escalator
Other:
- interferons
- complement
- lysozyme
- acute phase proteins
What general things can make someone more susceptible to infection?
- Extremes of age
- pregnancy
- malnutrition
What happens if the normal commensal flora in the gut are altered?
Antibiotic treatment can kill/alter the normal commensal flora in the gut
this increases susceptibility to C. Diff and Candida spp. Infections
Which infections are burns patients susceptible to?
Infections by pseudomonas and streptococcus
At which stage of infection are neutrophils important?
What happens if someone was to have less neutrophils?
Neutrophils are important after the initial breach of innate defences
if someone has less neutrophils, they have an increased risk of contracting an infection
What are the 2 categories of neutrophil defects and the differences between them?
Qualitative defects:
- this is when the neutrophils are present, but they don’t work properly
Quantitative defects:
- this is when there are not enough neutrophils present to be effective
What are examples of qualitative neutrophil defects?
Neutrophils lose the ability to kill or chemotaxis
- e.g. Inadequate signalling
- chronic granulomatous disease
What infection is someone with chronic granulomatous disease more susceptible to?
Staphylococcus aureus infection
What may quantative neutrophil defects lead to?
In which patients is this seen?
Neutropenia
this is a lack of neutrophils
- cancer treatment
- bone marrow malignancy
- aplastic anaemia from drug use
What is aplastic anaemia?
A rare disorder in which the bone marrow fails to produce enough blood cells
When is neutropenia particularly clinically important?
If neutrophil count is < 0.5 x 109
or
if neutropenia is prolonged over long periods of time
e.g. In AML patients who have neutropenia for weeks are at more risk of bacterial or fungal infections
What infection is particularly prominent in neutropenia patients?
>50% of neutropenia patients are prone to infection with high mortality
>50% of those with pseudomonas infections will die in 24 hours if they are not treated
What is the treatment for infection in neutropenic patients?
They are treated with a broad spectrum antibiotic which includes defence against pseudomonas
antipseudomonal penicillin +/- gentamicin
if first line treatment is not effective, the second line treatment is carbapenem
What opportunistic infection are neutropenia patients more susceptible to?
Infections with normal flora - coagulase negative staphylococcus
this is a low pathogenicity organism which can enter the blood
Which bacterial infections are more prominent in neutropenic patients?
E. Coli, Staphylococcus aureus
look for skin infections as chemotherapy can lead to ulcers and bacteraemia
Which fungal infections are neutropenic patients more susceptible to?
Candida spp. , aspergillus spp.
the spores will enter the alveoli and cause fungal pneumonitis
Why is it important to try and prevent infections in neutropenic patients?
What treatment can be used?
Cancer patients may need to have chemotherapy delayed due to infection
this can worsen the cancer outcome
granulocyte stimulating factors (GCSF) are used to try and prevent immunosuppression
What are the different types of T cell deficiencies?
Congenital:
- these are rare
- T helper dysfunction +/- hypogammaglobulinaemia
Acquired:
- drugs e.g. ciclosporin after transplantation and steroids
- viruses e.g. HIV
What opportunistic bacterial infections are T cell deficient patients susceptible to?
Listeria monocytogenes
this grows in fridge temperatures and comes from food such as Brie cheese
mycobacteria
Which viral infections are T cell deficient patients susceptible to?
What is the treatment?
Herpes viruses - herpes simplex, cytomegalovirus and varicella zoster
serological testing followed by prophylaxis and treatment with aciclovir and gangciclovir
What fungal infections are T cell deficient patients susceptible to?
Candida spp. , cryptococcus spp.
new patients with HIV usually present with cryptococcus meningitis
this has a thick capsule to help prevent it from phagocytosis
What is the difference with varicella zoster virus in a T cell deficient patient?
Shingles will be much more severe
this means that the skin is much more prone to secondary infection by staphylococcus aureus
Which protozoan/parasitic infections are T cell deficient patients more susceptible to?
Cryptosporidium parvum and Toxoplasma gondii
What are the characteristics of cryptosporidium parvum?
How is it treated and how long does it take to recover?
Oocysts are shed by cattle/humans into the water so it is spread via faecal-oral route
most patients recover after prolonged illness of up to 3 weeks
recovery takes much longer in T cell deficiencies
in most cases, only symptomatic treatment is used and antibiotics are not given
What is meant by hypogammaglobulinaemia?
What are the 2 different types?
This is having an antibody level below normal
Congenital:
- x-linked agammaglobulinaemia (rare)
Acquired:
- multiple myeloma
- burns
What is the treatment for hypogammaglobulinaemia?
Which bacteria and parasites tend to cause infection?
It is treated with immunoglobulin to replace the antibodies
it is encapsulated bacteria that cause problems e.g. streptococcus pneumoniae
the parasite that usually causes infection is giardia lamblia
What are the 2 forms of giardia lamblia?
What symptoms can it cause?
Trophozyte form:
- this is the form of the disease which is present in the water
cystic form:
- this is the form of the disease that is ingested
- it has a hard shell to stop it from drying out
It causes diarrhoea, fatty stools and can cause weight loss
What type of infections tend to be present in complement deficiency?
Encapsulated bacteria - complement is needed to help kill organisms
If the C5-8 section is deficient - Neisseria meningitidis is important
this is a gram negative coccus that causes meningitis
there are frequent serious S. Pneumoniae infections due to poor quality opsonisation
What can cause splenectomy?
The spleen is a source of complement and antibody producing B-cells
it removes opsonised bacteria from the blood
splenectomy can be caused by:
- Traumatic
- Surgical
- Functional asplenia e.g. sickle cell disease
What are the treatments for infections in splenectomy?
Which infections are common?
- S. Pneumoniae
- Haemophilus influenzae type B
- N. Meningitidis
- Malaria
these are mostly encapsulated organisms
these infections have high mortality and can be prevented through vaccination and prophylactic penicillin
What are biologics and how do they work?
They are antibodies or other peptides
they inhibit inflammatory cytokine signals e.g. tumour necrosis factor
this inhibits T cell activation and depletes B cells
they are used in severe rheumatoid arthritis
What are the risks associated with biologics
- Risk of tuberculosis
- Risk of herpes zoster
- Risk of legionella pneumonophilia
- Risk of listeria monocytogenes
What are the 2 types of organ transplantation?
What treatment is required afterwards and why?
Solid organ transplants - e.g. liver in paracetamol overdose
stem cells in haematological malignancy
anti-rejection treatment is needed to suppress cell mediated immunity
this stops the effects of cytotoxic and natural killer cells
What affects the degree of immunosuppression in organ transplants?
The degree of immunosuppression varies on how closely the donor and recipient are matched and the organ involved
What are the general principles for management of infection?
- Treat the known infection - need specimens from the likely site of infection to guide therapy
- remove catheters and lines
- reverse the defect if possible - stop immunosuppression - GCSF
- prevention is most important i.e. hand washing
What techniques can help in prevention of infection?
- Hand washing, aseptic technique, protective isolation, HEPA air filtration
- vaccines (avoid live in T cell deficient patients as this can cause infection)
- prophylactic antimicrobials and passive immunoglobulin
- special diets
In a febrile neutropenic, what treatment should be given?
Broad spectrum anitbiotics
piperacillin / tazobactam
What are the stages involved in treating candida infections?
Start antifungal therapy and remove any lines
give liposomal amphotericin B (broad spectrum antifungal) followed by fluconazole treatment
this is an oral agent given for 2 weeks after treatment
What is the treatment for lobar pneumonia?
Lobar pneumonia caused by streptococcus pneumoniae is treated with IV benzylpenicillin
