Crash Course Immunocompromised + Influenza Flashcards
Which organisms are patients with splenectomy susceptible to?
encapsulated organisms- NHS
Neisseria
Haemophilus
Streptococcus
What are 2 microbiological consequences of immunocompromise?
Infection with unusual organisms
Infection in unusual sites
Name 2 unusual organisms and 2 unusual sites of infection seen in HIV patients
Organisms:
Microsporidium: GI infection exclusively seen in HIV
MAC
Sites:
CMV colitis
Oesophageal candidiasis
What unusual organism are patients with CF susceptible to? What is the significance of this?
Burkholderia cepacia
CI to lung transplant
What organism causes an unusual site of infection in sickle cell disease patients?
Salmonella septic arthritis
What unusual organism are patients on monoclonals such as anti-TNF alpha susceptible to?
JC virus
What prophylactic measures can be taken for immunocompromised?
Pre-splenectomy: Vaccination against meningitis + pneumonococcus
HIV: Co-trimoxazole if CD4 <200
What is caused by reactivation of JC virus?
Progressive multifocal leukoencephalopathy
What is JC virus AKA?
Human polyomavirus 2
How many serovars of influenza? Which is worst?
4 serovars (C+D not clinically relevant)
A worse than B- more likely to cause pandemic
What 3 characteristics are required for a virus to cause a pandemic?
Novel antigenicity
Replicates efficiently in human cells.
Transmit efficiently between people.
What results in novel antigenicity?
Antigenic drift
Antigenic shift
What is antigenic drift?
Accumulation of mutations over time.
Error prone replication process, slightly different primary sequence for some of the proteins, happens relatively frequently, small changes accumulate
Why are new vaccines to influenza required each year?
Antigenic drift
Leads to production of new epidemic strain every year
Pre-formed antibodies from last exposure are not so effective.
What is antigenic shift?
Recombination of genomic segments of 2 co-infecting flu strains→ leads to rapid antigenic change+ production of new viral strain (shift)
Allows exchange of RNA segments between human + animal strains
Why does antigenic shift not happen often?
Rare for an organism to be co-infected with 2 strains of influenza
Often recombination produces nonsense
What is the natural reservoir of influenza A viruses?
A. Pigs
B. Chickens
C. Ducks
D. Tigers
Ducks
How is the viral genome of influenza composed?
8 “chunks” of RNA
What is Haemagglutinin? What is its function?
Protein on surface of influenza
Allows ENTRY: binds to sialic acid, cleaved by tryptase on surface of cells in lungs
What is haemagglutinin especially prone to? What is the significance of this?
Prone to antigenic DRIFT
Target this protein in yearly vaccine
What is Neuraminidase? What the function of Neuraminidase?
Protein on surface of influenza virus
Allows EXIT: Cleaves sialic acid
Facilitates viral release
What is neuraminidase more prone to?
Antigenic SHIFT process
What technique can determine virus and strain of influenza?
RT-PCR
(Reverse transcription polymerase chain reaction)
What is the most commonly used influenza antiviral?
Oral Oseltamivir
Neuraminidase inhibitor
Prevents viral release + thus replication + infection of other cells
Others: Inhaled Zanamivir + IV Peramivir
How do normal antivirals and ‘val-antivirals’ differ?
Usually same drug
Val- increases bioavailability + resistance to first pass metabolism
Can be taken less often to get up to therapeutic dose
Can be taken orally
What is the stepped treatment of HSV or VZV? (if previous step ineffective)
- Acyclovir
- Foscarnet
- Cidofovir
What is the stepped treatment of CMV or EBV?
- Ganciclovir
- Foscarnet
- Cidofovir
For non-herpes viral infections e.g. Adenovirus, what anti-viral should be used? What are the disadvantages of this?
Cidofovir
“Dirty drug”: Nephrotoxic, Ocular toxicity + BM suppression
What are the manifestations of HSV1?
Oral herpes: Herpes labialis
Initially may be HSV gingival-stomatitis in mouth
HSV encephalitis
What does reactivation of HSV1 usually cause?
Isolated vesicles + cold sores
What are the manifestations of HSV2?
Genital herpes
HSV meningitis
Which types of HSV virus infections are AIDS defining illnesses?
HSV oesophagitis, colitis or rarely pneumonitis
What is eczema herpeticum?
Disseminated herpes infection in those with atopic dermatitis
Usually kids with eczema
What is herpetic whitlow?
Herpes on the finger
Common in HCPs
In which patients is disseminated cutaneous herpes seen?
Immunocompromised
How does VZV commonly present?
In children with fever, malaise + rash
Rash starts on face, descends
Macules -> Papules -> Vesicles
List 4 serious complications that can arise from VZV in adults/ immunocompromised
Pneumonitis
Encephalitis
Myocarditis
DIC
What is caused by reactivation of VZV?
Herpes zoster: Shingles- dermatomal rash
What is Ophthalmic herpes zoster?
Shingles of V1 (1st branch of trigeminal nerve)
Can damage retina
Specific sign: Hutchinson sign- vesicles on tip of nose
Emergency- send to ophthalmologist
What is Ramsay Hunt syndrome?
Shingles affecting facial nerve
Ear pain
Facial paralysis
Vesicles usually in ear
Requires prompt Tx
Which medication should NOT be given in VZV infection?
Ibuprofen
Esp. in children
Increases risk of secondary skin infections + necrotising fasciitis
Name one complication of shingles
Herpetic neuralgia
Pain in distribution of that dermatome
How does Epstein-Barr virus present?
Presents with infectious mononucleosis:
Fever
Pharyngitis
Lymphadenopathy (usually symmetrical, posterior cervical chain)
Hepatitis
+/- Splenomegaly
Give 3 investigations for EBV
EBV serology
Atypical lymphocytes
Heterophile antibody (monospot test)
Name 2 infections other than EBV that can cause infectious mononucleosis
CMV
Toxoplasmosis
What is the management of EBV?
Not much evidence for using antivirals
Avoid contact sports
Avoid alcohol (have hepatitis)
If very fulminant EBV, what drug may be considered?
Ganciclovir
Why must high contact sports be avoided in EBV?
Splenomegaly- increases risk of splenic rupture
What malignancy is EBV associated with?
Nasopharyngeal carcinoma
Burkitt’s lymphoma
Where does EBV remain dormant?
B cells
What occurs in EBV post-transplant lymphoproliferative disease?
- Immunosuppression for transplant
- Once immunosuppressed lose surveillance of EBV
- Leads to pre-lymphoma state
- Needs intervention or will progress to lymphoma
How does Cytomegalovirus present?
Typically Asymptomatic
or
Infectious mononucleosis picture
Where does Cytomegalovirus live dormantly? How is it visualised?
Monocytes + Dendritic cells
Owl’s Eye inclusion bodies
Give 4 manifestations of CMV reactivation in immunosuppressed individuals
Pneumonitis
Retinitis
Colitis
Encephalitis
What is firstline treatment for CMV?
Ganciclovir / Valganciclovir
How does CMV pneumonitis appear on imaging?
ground glass appearances
multifocal
widespread
Give 1 feature of CMV retinitis on fundoscopy
Cotton wool spots difusely
What are the manifestations of HHV6 and HHV7?
Principally causes ROSEOLA
very very rarely encephalitis
How does HHV8 manifest?
Only seen in immunosuppressed, esp. HIV
Lymphoproliferative diseases:
Kaposi’s Sarcoma
Castleman disease
Primary effusion lymphoma
Where do Kaposi Sarcoma lesions occur?
Skin
Internally esp. resp + GI tract: can haemorrhage severely
What is the treatment of kaposi sarcoma?
Treat immunosuppression + immune system should clear the cancer
Give 4 manifestations of Adenovirus in immunosuppressed individuals
Pneumonitis/ pneumonia
Haemorrhagic cystitis
Meningioencephalitis
Colitis
What occurs in JC virus in immunocompromised?
Can reactivate in brain causing Progressive Multifocal Leukoencephalopathy
(resistant to antivirals)
In which patients is BK virus worrying?
Transplant patients
What does BK virus cause in renal transplant and bone marrow transplant patients?
Renal: BK virus infects transplanted kidney: Nephropathy
BM: Haemorrhagic cystitis
