Infection and Immunology

Question 1

what is the most common cause of candidiasis?

Answer 1

candida albicans

Question 2

Risk factors for candidiasis infection?

Answer 2

Broad-spectrum antibiotics
immunocompromise - HIV, steroids (oral or inhaled)
DM

cushing’s
GI tract surgery
central line

Question 3

What are the features of oral candidiasis?

Answer 3

common in neonates
a curd-like white patches on the mouth which can be REMOVED EASILY showing a red base

Question 4

what are the features of oesophageal candidiasis?

Answer 4

dysphagia +/- pain on swallowing
white patches on OGD

it is an AIDS DEFINING ILLNESS

Question 5

what does candidiasis of the skin look like?

Answer 5

sore + itchy
red, moist skin with ragged peeling edge
might have papules and pustules

Question 6

Name an anti-fungal which might be used to treat candidiasis?

Answer 6

fluconazole

Question 7

what is cellulitis?

Answer 7

it is an acute non-purulent spreading infection of the sub-cutaneous tissue

Question 8

what are the most common causative organisms of cellulitis?

Answer 8

Streptococcus pyogenes 
staphylococcus aureus (beware of MRSA)

Question 9

what is the cause of orbital cellulitis?

Answer 9

haemophilia influenzae

Question 10

what are the RF for cellulitis?

Answer 10

skin break
poor hygiene
poor vascularisation of tissue

Question 11

what is the cause of HSV encephalitis?

Answer 11

HSV 1 usually

Question 12

What are the symptoms of HSV 1?

Answer 12

primary = usually asymptomatic. gingivostomatitis, pharyngitis, herpetic whitlow (finger lesion)
lymphadenopathy (tender)

secondary = perioral tingle -> vesicles -> ulcer + crust -> healed 8-10 days alter

may cause herpetic encephalitis

Question 13

what are the symptoms of HSV 2?

Answer 13

painful blister/rash in genital, peri-genital or anal area
MACULOPAPULAR RASH

dysuria
fever
malaise
inguinal lymphadenopathy

Question 14

how is HIV transmitted?

Answer 14

through exchange of bodily fluids

sexual intercourse, mother-to-child, needle sharing/stick injuries, blood transfusions, organ transplantations

Question 15

what is the pathophysiology of HIV?

Answer 15

HIV enters CD4+ lymphocytes via GP120 receptors -> reverse transcriptase enables HIV genetic material to be added to host genome

cells produce more HIV -> dissemination -> cell death and eventual T cell depletion.

Question 16

what are the three phases of HIV?

Answer 16

1. seroconversion
2. early/asymptomatic
3. AIDS

Question 17

what are the features of stage 1 of HIV?

Answer 17

self-limiting stage

fever, night sweats, general lymphadenopathy, sore throat

other: oral ulcers, rash, myalgia, headache, encephalitis, diarrhoea

Question 18

what are the features of stage 2 of HIV?

Answer 18

early/asymptomatic

usually appear well, may have persistent lymphadenopathy, progressive minor symptoms (rash, weight loss, oral thrush)

Question 19

what are the features of stage 3 of HIV?

Answer 19

AIDS

secondary diseases due to immunodeficiency

Question 20

what are some of the secondary effects arising from the immunodeficiency caused by HIV?

Answer 20

bacterial infections, viral infections (CMV, HSV, VZV, HPV, EBV)

fungal infection - pneuomocystic jirovecii pneumonia, cryptococcus, candidiasis, aspergillosis

protozoal - toxoplasmosis

tumour - kaposi sarcoma, SCC, both lymphomas

Question 21

what kind of a virus is EBV?

Answer 21

a gamma-herpes virus (dsDNA)

Question 22

how is EBV transmitted?

Answer 22

it is found in pharyngeal secretions of an infected individual

close contact leads to spread (e.g. kissing, sharing eating utensils)

Question 23

what is the pathophysiology of EBV?

Answer 23

infection of epithelial cells in oropharynx -> infects B cells -> they disseminate the disease -> humoral and cellular immune response across the body -> primary infection ends but virus is latent in B cells

reactivation of latent virus in B cells after stress of immunosuppression

atypical lymphocytes can be detected on blood film

Question 24

what happens if patients with EBV are given ampicillin or amoxicillin?

Answer 24

develop a widespread maculopapular rash

Question 25

what is the investigation to test for EBV?

Answer 25

heterophile antibody test

Question 26

what would you expect from your investigations to confirm EBV?

Answer 26

+ve heterophile antibody test
leucocytosis
raised AST/ALT
peripheral blood film showing abnormal leucocytes

Question 27

what are the signs of EBV?

Answer 27

pyrexia
cervical/generalised lymphadenopathy
splenomegaly
hepatomegaly
erythematous + oedematous pharynx, exudate on tonsils
jaundice in 5-10%

Question 28

how do you manage EBV?

Answer 28

nsaids + paracetamol, bed rest
avoid contact sport for 2/52 due to splenic rupture risk
steroids for severe cases

Question 29

what is the most severe form of malaria?

Answer 29

infection with plasmodium falciparum

Question 30

briefly describe the life cycle of plasmodium

Answer 30

1. injection of sporozoites from FEMALE mosquite into blood
2. invasion + replicate in hepatocytes
3. re-enter blood and infect RBC
4. replicate in RBC developing ring forms
5. RBC rupture, release merozoites -> infect more RBC
6. new mosquite bites and takes up gametocytes
7. gametocytes -> sporozoites in mosquite gut -> move to saliva ready to reinfect

Question 31

what populations have a degree of innate immunity to malaria?

Answer 31

sickle cell trait
G6PD Deficiency
pyruvate kinase deficiency
thalassaemia

Question 32

What is the maximum incubation period for malaria?

Answer 32

up to a year

need to establish patient travel history a year prior to presenting to healthcare professionals if suspecting malaria

Question 33

what investigations are performed if you suspect malaria?

Answer 33

thick and thin blood film (thick for quantifying, thin to identify plasmodium species)

bloods: FBC (haemolytic picture), LFTs, U&Es, ABG
urinalysis for haematuria or proteinuria

Question 34

what are the signs of malaria?

Answer 34

pyrexia
anaemia (haemolytic)
hepatosplenomegaly

Question 35

what are the symptoms of malaria?

Answer 35

cyclical

high fevers, flu-like symptoms (fatigue, muscle ache, abdo/back pain), sweating, shivering cold/rigors, nausea + vomiting, headache

Question 36

how is VZV transmitted?

Answer 36

aerosol inhalation or direct contact with vesicular secretions

Question 37

where is the dormant VZV found?

Answer 37

dorsal root ganglion

Question 38

what are the features of primary VZV infection?

Answer 38

CHICKENPOX

prodromal malaise, mild fever, intense itchy rash spreading affecting mainly face and trunk, vesicles weep + crust

infections from 48 hrs before rash till vesicles have crusted (7-10 days)

MACULOPAPULAR RASH, skin excoriation, mild fever

Question 39

what are the features of secondary VZV infection?

Answer 39

tingling/hyperaesthesia in dermatomal distribution
painful skin lesions + rash in dermatomal distribution

vesicular maculopapular rash over a dermatome

recovery 10-14 days

Question 40

What is Ramsey-hunt syndrome?

Answer 40

VZV secondary infection in the geniculate ganglion

causes zoster in ear and facial nerve palsy (LMN). vesicles may be visible behind the pinna of ear canal

Question 41

what is the definition of sepsis?

Answer 41

Sepsis is life-threatening organ dysfunction caused by dysregulated host response to an infection.

Question 42

what are the components of SIRS? (not needed for sepsis)

Answer 42

• 2 or more of:
  
  • Temperature < 36 or > 28
  • Heart rate > 90 bpm
  • RR > 20 or PaCO2 < 4.5 kPa or mechanically ventilated
  • WBC < 4 or > 11 or > 10% immature forms

Question 43

describe qSOFA

Answer 43

quick screening, > 2 associated with high risk of mortality and requirement for ICU

• RR > 22
• altered mentation (GCS < 15)
• systolic BP < 100mmHg