Microbial typing
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This document discusses techniques for differentiating between strains of microorganisms based on their phenotypic and genotypic differences, known as typing. Phenotypic techniques detect expressed characteristics, while genotypic techniques analyze genetic elements directly. Some common typing techniques mentioned are biotyping, phage typing, serotyping, antibiogram typing, plasmid analysis, restriction endonuclease analysis, pulsed-field gel electrophoresis, and nucleotide sequence analysis.
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.