Epidemiological marker-(Phenotype and Genotype)

Gaurab Karki — Sat, 15 Aug 2020 05:30:34 +0000

Characteristics of epidemiological marker:

Phenotyping method is based on the expressed characteristics.
Characteristics of organism that is used for typing is marker.
Organism of same source origin or source- type/strain.
Phenotyping includes;
- Biotyping
- Serotyping
- Phage typing
- Antibiogram typing
- Bacteriocin typing
Biotyping:
- Classified on the basis of physiological or bio-chemical tests.
- Commonly used characters are morphology, cultural characteristics, biochemical reactions (nitrate reduction test, indole test, pigment production, H₂S production, carbohydrate fermentation)
Serotyping:
- Typing method done by the use of hyper-immune anti-sera or purified immunoglobulin to detect specific antigen.
- Serotyping is generally done for Salmonella, Klebsiella, etc. for detection of O-antigen, H-antigen, R-antigen, K-antigen, etc.
Phage typing:
- Bacteriophage typing identify strains by the pattern of specific set of phages.
- Generally used for Staphylococcus aureus and for Salmonella Typhi.
Antibiogram typing:
- Typing method on the basis of antibiotic susceptibility or resistance pattern.
Bacteriocin typing:
- On the basis of bacteriocin production.

Genotyping includes;
- Plasmid profiling
- G+C ratio
- Ribotyping
- Restriction endonuclease
- RPLP
- PFGE
- PCR amplification
Plasmid profiling:
- On the basis of no. of plasmid, size of plasmid in the organism.
G+C ratio:
- Same strains have similar G+C ratio.
Ribotyping:
- 16sRNA is highly specific for organism.
Restriction endonuclease enzyme:
- Whole genome is fragmented using same set of restriction endonuclease enzyme and analyzed.
RFLP (Restriction fragment length polymorphism):
- Particular enzyme is used to fragment whole genome.
PFGE (Pulse field gel electrophoresis):
- Electric field is applied diagonally in two field.
- The electric field is applied and then pulsed and re-applied perpendicularly.