Rapid Microbiological Method

Enzyme Link Immnosorbent Assay ( ELISA)

After Enrichment and isolation of the target pathogen, Antigen from the isolate is being release into a well (Vessel) containing antibody against specific pathogen’s antigen. Antigen-Antibody complex forms.

An enzyme is dispense into the well and will bind specifically to Antigen-Antibody Complex.

An Enzyme substrate is then added to the vessel.

If the enzyme has bind to the Antigen-Antibody Complex, enzyme will bind to enzyme substrate, catalysing a particular reaction to the substrate, which will yield a colour.

The presence of such colour can be correlated to the presence of pathogen.

This method may be used for many pathogens like salmonella spp.

Genetic Method

After Enrichment and isolation of the target pathogen, cell undergoes cell lysis.
Cell lysis causes the microbes cell to rapture and release the DNA .
Endonuclease is added to cleave the desired set of gene on the DNA, which is unique to a particular microorganism.

PCR: Addition of DNA Polymerase will make copies of that Gene to a detectable level by electrophoresis.

After PCR reaction, Agarose Gel electrophoresis will separate the DNA fragments into bands. The bands are then compared against the known / target pathogens DNA fragment bands to check for the presence of that pathogen.

This method is also use to detect GM food.

For more information, please see Sarah’s and Farziana’s blog, also Dip. In Biotech notes Molecular Biology.