Microbial typing

1. Dr Vinodh Kumar,O.R
Division of Epidemiology
ICAR-Indian Veterinary Research Institute
Izatnagar, Uttar Pradesh, India

2. Analyse multiple isolates
within a given species
Study the small differences
between the same species.
 In epidemiological
studies, and to study the
pathogenesis of infection.
The process of
differentiating strains
based on their
phenotypic and
genotypic differences is
known as 'typing'.

3. Phenotypic techniques
detect characteristics expressed by the microorganism
Genotypic techniques
direct DNA-based analysis of chromosomal or
extrachromosomal genetic elements

4. Based on size, staining properties, biochemical
properties and antigenic properties
Biotyping
Phage typing
Bacteriocine typing
Serotyping
Antimicrobial Susceptibility Typing (Antibiogram):
Protein typing
Multilocus Enzyme Electrophoresis (MLEE)

5.  Based on study of the microbial DNA, the
chromosome and plasmid, their composition,
homology and presence or absence of specific genes
Plasmid analysis
Restriction Endonuclease Analysis
PFGE of Chromosomal DNA
Southern blot analysis
Nucleotide Sequence Analysis

6. Metabolic activities expressed by an isolate, colonial
morphology and environmental tolerances
Manual or automated
referred as ‘biotypes’

7. Based on the pattern of resistance or susceptibility to
a standard set of bacteriophages
 referred as ‘phage types’

8.  Based on the susceptibility to a set of bacterial
peptides (bacteriocine) produced by certain bacteria.
Bacterocines produced by a particular strain are
usually only active against other strains of the same
species.

9.  Based on antigenic determinants expressed on the
cell surface
referred as ‘Serotypes’

10.  Based on comparison of different isolates to a set of
antibiotics

11. Based on major or minor differences in the range of
proteins made by different strains
comparisons among multiple strains are difficult

12. The isolates are analysed for differences in the
eletrophoretic mobilities of a set of metablolic
enzymes
referred to as ‘electromorph’

13.  Based on the number and sizes of plasmids carried by
an isolate
Can be determined by preparing a plasmid extract
and subjecting to gel electrophoresis

14. A restriction endonuclease enzymatically cuts DNA at
a specific nucleotide recognition sequence
Bacterial DNA is digested with endonucleases that
have relatively frequent restriction sites

15. A variation of agarose gel electrophoresis
The orientation of the electric field across the gel is
changed periodically
Large fragments can be effectively separated by size

16. Detect only the particular restriction fragment
fragments transferred to nitrocellulose membranes
and detected by labelled DNA probes
Variations in the number and sizes of the fragments
Ribotyping:
 Blotting of restriction enzyme digestion of rRNA,
and one or more tRNAs

17. Genotype information
Automated techniques to sequence
Possible to compare multiple isolates.