Electron Microscopy and Viruses

The Forgotten Diagnostic ToolSue Alderson

Scientific Officer

Introduction

The Electron MicroscopeHistoryRequirements Advantages and DisadvantagesSpecimen Types and Viruses DetectedThe Future

History

Poxvirus – 1938Smallpox and VZV in late 1940’sNegative staining – late 1950’sHendra and Menangle virus – 1995SARS Coronavirus 2003Melaka virus 2006

Requirements

Should be quality controlledSwabs unsuitableNeed 106-108 particles/mLConcentrate specimen

Advantages

Simple and rapid No prior knowledge of virus requiredNo reagent selection

Disadvantages

Low sensitivity and specificity – may be enhanced by IEMAnalysis based on morphology onlyExpensive equipmentExpensive maintenanceExperienced technicianNot suitable for large numbersWrong specimen collection

SpecimensFaeces RotavirusAdenovirusEnterovirusCoronavirus-like particles (CVLP)AstrovirusCalicivirusNorovirusReovirusSRVLPHepatitis A and E

Specimens

Skin scrapings and vesicle fluidPoxvirusWart virusHSV and VZV

Specimens

RespiratoryMyxovirusesSRVAdenovirusHerpesvirusesCoronavirus

Specimens

TissuesUrineCSFCell culture

The Future (1)

Emergent SituationsFrontline methodCo-ordinated and run in parallel with other diagnostic testsMorpho-diagnosis allows treatment and containment

The Future (2)

BioterrorismAssist in poxvirus diagnosis and/or rule out other cause of rash illnessCannot distinguish between poxvirusesRequires BSL-2 containment with BSL-3 precautions

Conclusion

Don’t forget…

Electron microscopy is still a valuable diagnostic tool when combined with

other testing methods!