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