Chapter: Microbiology and Immunology: Laboratory Identification of Bacteria and Taxonomy

Typing of Bacterial Strains

The ability to discriminate between similar strains of bacte-ria may be important in tracing sources or modes of spread of infection in a community.

Typing of Bacterial Strains

The ability to discriminate between similar strains of bacte-ria may be important in tracing sources or modes of spread of infection in a community. Typing methods are widely used for epidemiological studies. These include (a) phenotypic techniques and (b) genotypic techniques.

◗ Phenotypic techniques

Phenotyping techniques depend on various observable properties of bacteria, which are discussed as follows:

· Biotyping: It relies on a set of biochemical reactions to dis-tinguish different strains within a given species. Antimicro-bial susceptibility testing is an example of this type.

· Serotyping: Different strains of organisms of the samespecies can be differentiated based on the difference in the expression of antigenic determinants on the cell surface.

· Bacteriocin typing: This is used in case of bacterial species forwhich a number of lytic bacteriophages have been identified.

· Phage typing: This has been the mainstay of strain discrim-ination and is widely used in epidemiological studies.

◗ Genotypic techniques

Genotypic techniques depend on differences related to the genome of bacteria. Genotypic techniques employed to differentiate strains of bacteria include plasmid profile analysis and restriction endonuclease analysis of chromosomal DNA.

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Microbiology and Immunology: Laboratory Identification of Bacteria and Taxonomy : Typing of Bacterial Strains |