Systems for Detection of Pathogens Flashcards Preview

Sem 4: TI2 > Systems for Detection of Pathogens > Flashcards

Flashcards in Systems for Detection of Pathogens Deck (10):

What are commensal non-pathogens, zoonotic non-pathogens and commensal opportunists?

  • Commensal non-pathogen - present but not capable of causing disease in host. 
  • Zoonotic non-pathogen - present but only capable of causing disease in another host - e.g. E. coli subclinical in cattle but pathogenic to humans. 
  • Commensal opportunist - present and capable of causing disease in the host, but only in certai circumstances. 


Define a pathogen. 

A microbe capable of causing a specific degree of host damage under certain circumstances. 


Describe the advantages and disadvantages of microscopy in pathogen detection. 


  • Easy to perform. 
  • Rapid screening. 
  • Some parasites have specific morphology. 


  • Not sensitive. 
  • General stains are not specific. 
  • Expensive - labour intensive, requires specialist interpretation. 


What conditions can we control in order to select for a specific microbe?

  • Selective media
  • Selective temperature
  • Selective atmosphere 
  • Antibiotics - e.g. using ampicillin resistance gene


Describe the advantages and disadvantages of classical culture. 


  • Cheap, simple, reliable reagents. 
  • Sensitive - single organisms grown and identified. 
  • Validated specificity. 
  • Direct in vivo measurement of effectiveness of therapy - e.g. antibiotic sensitivity. 


  • Some pathogens cannot be grown. 
  • Some pathogens cannot be well differentiated by biochemistry alone. 
  • Slow - culture requires at least overnight incubation.
  • Some pathogens grow slowly to aid rapid diagnosis. 
  • Expensive - labour intensive and requires specialist interpretation. 


What are the advantages of using microarrays?

  • Covers the whole genome. 
  • Can be used for RNA and transcriptomics. 
  • Can look for microRNA. 


Name 4 genetic techniques for detection of pathogens. 

  • Gene targeting 
  • Genome targeting 
  • Targeting biomarkers of virulence
  • Rapid sequencing


Describe the advantages and disadvantages of mass spectrometry (MALDI-TOF) in pathogen detection. 




  • Can only identify a known profile. 


Describe the advantages and disadvantages of using biomarkers of virulence to detect pathogens. 


  • Good specificity. 
  • Good sensitivity. 
  • Easily automated. 


  • Serological response not rapid - not useful in acute infections.
  • Single sera results are meaningless due to possible previous exposure. 
  • Some antibodies are cross-reactive. 
  • Virulence is only inferred by the presence of a biomarker - not proven. 


Describe the advantages and disadvantages of using molecular detection methods to identify pathogens. 


  • Faster than traditional techniques. 
  • Allows for timely therapy and interventions. 
  • Increased sensitivity in positive samples. 
  • Can be automated and has potential for point of care testing. 


  • Expensive - labour intensive, requires expertise. 
  • Does not screen for unknowns. 
  • Possibility of contamination. 
  • Negative samples may still need culture.