microbial typing
TRANSCRIPT
Dr Vinodh Kumar,O.RDivision of Epidemiology
ICAR-Indian Veterinary Research InstituteIzatnagar, Uttar Pradesh, India
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'.
Phenotypic techniquesdetect characteristics expressed by the
microorganism
Genotypic techniquesdirect DNA-based analysis of chromosomal or
extrachromosomal genetic elements
Based on size, staining properties, biochemical properties and antigenic properties
BiotypingPhage typingBacteriocine typingSerotypingAntimicrobial Susceptibility Typing
(Antibiogram):Protein typingMultilocus Enzyme Electrophoresis (MLEE)
Based on study of the microbial DNA, the chromosome and plasmid, their composition, homology and presence or absence of specific genes
Plasmid analysisRestriction Endonuclease AnalysisPFGE of Chromosomal DNASouthern blot analysisNucleotide Sequence Analysis
Metabolic activities expressed by an isolate, colonial morphology and environmental tolerances
Manual or automated referred as ‘biotypes’
Based on the pattern of resistance or susceptibility to a standard set of bacteriophages
referred as ‘phage types’
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.
Based on antigenic determinants expressed on the cell surface
referred as ‘Serotypes’
Based on comparison of different isolates to a set of antibiotics
Based on major or minor differences in the range of proteins made by different strains
comparisons among multiple strains are difficult
The isolates are analysed for differences in the eletrophoretic mobilities of a set of metablolic enzymes
referred to as ‘electromorph’
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
A restriction endonuclease enzymatically cuts DNA at a specific nucleotide recognition sequence
Bacterial DNA is digested with endonucleases that have relatively frequent restriction sites
A variation of agarose gel electrophoresisThe orientation of the electric field across the
gel is changed periodicallyLarge fragments can be effectively separated
by size
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
Genotype informationAutomated techniques to sequencePossible to compare multiple isolates.