Infectious Disease ICM

Question 1

How is HSV investigated?

How are results interpreted?

Answer 1

PCR on various sample types - CSF, swabs, vesicle fluid, BAL

HSV serology - clotted blood

detection of HSV found on both PCR and serology

Question 2

VZV Investigations?

Answer 2

chickenpox presentation is a clinical diagnosis - not typically lab diagnosis

• Can PCR the vesicle fluid
• serology - VZV IgG helps to establish status of infection
• In cases of meningitis/encepahlitis - PCR CSF

Question 3

CMV Investigations?

Answer 3

Bloods - FBC, serum creatinine and raised LFTs

IgG and IgM serology

CXR - pneumonitis presentation

USS - hepatits presentation

colonscopy - Coilitis presentation

Biopsy - CMV Coilitis , vitrous fluid in retinitis presentations

Histology - ‘owls eye’ inclusiins in infected cells

In hiv/aids - qualitative PCR

Question 4

EBV investigations and findings?

which Ix is diagnostic?

Answer 4

Bloods - lymphocytosis, raised LFTs and positive monospot test

ENT culture - isolated strep oralis

Virology - IgM/IgG , Resp PCR negative

monospot test is diagnostic - done in the 2nd week of a suspected EBV infection

Question 5

Investigations involved in lyme disease?

Answer 5

if presence of erythema migrans = clinical diagnosis

If rash not present - offer ELISA

• is neg but symptoms persist repeat test in 4-6wks
• if positive offer a immunoblot test

immunoblot is also offered to those with 12wks of symptoms with prev neg ELISA test

if positive on Immunoblot - diagnose with Lyme disease and offer antibiotics

Question 6

Mumps investigations? Findings?

Answer 6

mumps parotitis - clinical diagnosis

other presentations - IgM (positive in acute infections), IgG, and CSF/Saliva PCR - RNA detected

Question 7

Measles investigations?

Answer 7

IgM and IgG
saliva - IgM & PCR
PCR - throat swab, urine - RNA detected
if Suspected SSPE - CSF and brain biopsy PCR

Question 8

Parvovirus B19 Ix?

Answer 8

often clinically diagnosed

IgM/IgG
FBC - including reticulocyte count

Question 9

Group B strep (GBS) Ix?

Answer 9

bloods - FBC = lymphocytosis, neutropenia and thrombocytpenia

Biochem - glucose, electrolytes, creatinine, LFTs and CRP

CSF - glucose & protein

Microbiology - Blood cultures

Question 10

Listeria Monocytogenes ix?

Answer 10

FBC - leukocytosis and thrombocytopenia

blood culture

CSF - gram stain, MCS, glucose, protein
- if CNS involvement present CT/MRI

Stool culture

RARE - amniotic/foetal fluid or placental culture

If endocarditis suspected - echo

Question 11

Toxoplasmosis Ix? findings?

Answer 11

Serology - IgM & IgG
IgM - acute/very recent infections

PCR - DNA detected

hiv/immunocompromised - CT - single/multiple ring enhancing lesions
- mass effect may be seen

Question 12

Cyrptococcosis Ix? Findings?

which is Gold standard?

Answer 12

serum crytococcal Ag - lateral flow test

CSF microscopy - encapsulated yeast

Biopsy/histology

imaging = CXR, CT & MRI brain

GS = culture - india ink stain of CSF/Sputum

Question 13

Histoplasmosis Ix? Findings?

Answer 13

histology and cytology
sputum culure
Ag can be detected in serum/urine

Question 14

Pneumocystis Jiroveci Ix? Findings?

Answer 14

bloods - neutropenia, raised CRP, CD4, panhypogammaglobulinemia

CXR - usually normal, in some cases bilateral interstitial pulmonary infiltrates

Sputum sample - PCR, P.jiroveci detected

exertional destaurations

Question 15

salmonella Ix?

Answer 15

stool MCS

in cases of enteric/typhoid fever - Blood cultures and Stool MCS
- Serology often unreliable

Question 16

Shigella Ix?

Answer 16

stool MCS

Question 17

Tetanus Ix?

Answer 17

usually a clinical diagnosis

Question 18

Cholera Ix?

Answer 18

largely clinical diagnosis

stool MCS can be done

Question 19

Diphtheria Ix?

Answer 19

nose/throat swabs - microscopy and culture

Question 20

Botulism Ix?

Answer 20

usually clinical diagnosis

anaerobic cultures may be done

Question 21

Atypical Mycobacterial Disease?

Answer 21

mycobacterial cultures

in resp infections - sputum/BAL (AAFB tests and MCS)
- nodular change/cavities - CXR/CT

Question 22

Threadworms Ix & Dx?

Answer 22

usually clinical suspicion and diagnosis

- cellotape test

Question 23

Hookworms Ix & diagnosis?

Answer 23

stool OVP

Question 24

Amoebiasis Ix & Dx?

Answer 24

stool OVP, microscopy/PCR, amoebic serology and USS Liver

Question 25

Malaria Ix?

Answer 25

geisma stained blood film/smear
Rapid detection tests RDTs
FBC - anaemia, thrombocytopenia
LFTs - transaminitis

Question 26

notifiable diseases?

Answer 26

Botulism 
Cholera 
Diphtheria 
Enteric fever 
malaria 
measles 
mumps rubella 
tetanus

Question 27

Sepsis recognition & Diagnosis?

Answer 27

1. Administer oxygen: Aim to keep saturations > 94% (88-92% if at risk of CO2 retention e.g. COPD)
2. Take blood cultures
3. Give broad spectrum antibiotics
4. Give intravenous fluid challenges: NICE recommend a bolus of 500ml crystalloid over less than 15 minutes
5. Measure serum lactate
6. Measure accurate hourly urine output