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Micro - Bacterial Genetics (ii) (Bacterial Identification (molecular…

- - - - go to recipient cell + complementary stains is synthesised
  - - - mobile genetic elements
      - DNA sequences that move between chromo + plasmid in same cell
      - e.g. insertion sequence
        
        simplest
        
        carries the enzyme it needs to move (tranposase)
        
        random insertions cause gene disruption
      - often contain antibiotic resistance genes + virulence factors (e.g. Shiga toxin for E Coli)
- - - - amplification of a specific DNA sequence for observing + sequencing
      - NAAT
      - needed: dNTPs, oligonucleotide primers, Taq pol (thermus aquaticus, thermodynamically stable)
      - benefits: fast, easy, v sensitive, good for fastidious pathogens (e.g. TB, cryptococcus neoformans)
      - disadvantages: expensive, not always necessary, sensitive to contamination, PCR inhibitors in some biological fluids (e.g. blood), doesn't distinguish between dead + alive DNA, so use RT-PCR (DNA stable after death, but RNA only present in an alive cell)
      - uses: rapid detection of C diff + A fumigatus, quantifying HIV viral load, MecA detection (MRSA)
      - must have specific target
        
        specific gene
        
        universal 16S rRNA gene (in all bacteria, but exact sequence varies)
    - - based on genetic code
      - NB outbreak management - finding source
      - fast, accurate
      - multiple methods...
        
        PCR
        
        PFGE (pulsed field gel electrophoresis)
        
        DNA fragmented using restriction enzymes
        
        placed in agarose gel
        
        compare
        
        whole genome sequencing