Diagnostic methods

Question 1

Traditional methods

Answer 1

Culture - long time, many/most can’t grow
Staining - insensitive (100,000/mL)
Serology (immune response) - weeks, dependent on immune system
- still used for some (ex syphilis)

Question 2

Advantages of molecular methods

Answer 2

Sensitive to small numbers
Fast (in theory, in practice there are logistical barriers)
Detects organisms that can’t be cultured
Multiplex -> multiple organisms

Question 3

Disadvantages of molecular methods

Answer 3

Must know nucleic acid sequence
Need to distinguish between colonization and disease
Exclude false positives (small amount contamination)
May not actually be fast due to batching

Question 4

Amplification techniques

Answer 4

PCR
TMA - transcription mediated amplification
LCR - ligase chain reaction
bDNA - branched chain DNA amplification

Question 5

Molecular formats

Answer 5

Qualitative - large amplification
 - sensitive to small numbers
 - colonization/presence may not correlate to disease
Quantitative = graded signal
 - use to follow therapy
 - distinguish carrier from pathogen

Question 6

Other identification methods

Answer 6

Hybridization in solution
PCR and sequencing
Rapid FISH
Epidemiology via pulsed,field gel electrophoresis, restriction fragments, sequencing