Phage typing

Phage typing - Dr.SS

1. Microbial Taxonomy and Diversity – Phage typing Dr. S. Sivasankara Narayani Assistant Professor Department of Microbiology Ayya Nadar Janaki Ammal College Sivakasi 09/10/20 Dr.SS

2. UNIT – III CLASSIFICATION OF VIRUS Viruses: Physical, chemical and biological properties. Baltimore classification. Types of viruses based on structure and Host. Cultivation of viruses: Cell line - embryonated eggs - cytopathic effect. Structure of viruses: TMV- T4bacteriophage. Replication of virus: Lytic and lysogenic cycle. Phage typing. 09/10/20 Dr.SS

3. Phage Typing 09/10/20 Dr.SS

4. Typing system evaluation criteria Typeability Capacity to produce clearly interpretable results with most strains of the bacterial species Reproducibility Capacity to repeatedly obtain the same typing profile result with the same bacterial strain Discriminatory power Ability to produce results that clearly allow differentiation between unrelated strains of the same bacterial species Practicality (ease of performance & interpretation) Method should be versatile, relatively rapid, inexpensive, technically simple and provide readily interpretable results Laboratory Training for Epidemiologists Laboratory Training for Field Epidemiologists

5. Teichoid acid Lipoteichoic acid Capsule Polysaccharides Fimbirae (M-protein) Different Enzymes Peptidoglycan Phenotype & genotype bacteria PHENOTYPE GENOTYPE (Chromosomal & plasmid DNA) Laboratory Training for Epidemiologists Laboratory Training for Field Epidemiologists 09/10/20 Dr.SS

6. Typing methods Phenotypic Rely on expression of phenotypic characteristics (genetically coded) Antibiotic resistance, antigens etc. Genotypic Analysis of the genetic material DNA, RNA Laboratorz Training for Epidemiologists Laboratory Training for Field Epidemiologists 09/10/20 Dr.SS

7. Phenotypic techniques Serotyping Phage typing Antimicrobial resistance monitoring Multilocus enzyme electrophoresis (MLEE) Other: Protein profiling – SDS PAGE, immunoblotting Based on nutritional requirement e.g. auxotyping Biotyping Bacteriocin typing Laboratory Training for Epidemiologists Laboratory Training for Field Epidemiologists 09/10/20 Dr.SS

8. Phage typing Phage typing  is a method used for detecting single  strains  of  bacteria . It is used to trace the source of outbreaks of infections.  The  viruses  that infect bacteria are called  bacteriophages  (" phages " for short) and some of these can only infect a single strain of bacteria. These phages are used to identify different strains of bacteria within a single species. A culture of the strain is grown in the agar and dried. A grid is drawn on the base of the  Petri dish  to mark out different regions. Inoculation of each square of the grid is done by a different phage. The phage drops are allowed to dry and are incubated: The susceptible phage regions will show a circular clearing where the bacteria have been lysed, and this is used in differentiation. Spotted onto the confluence growth of bacteria 09/10/20 Dr.SS

9. Cont.. Phage is virus which live in a living cell. Bacteriophage: is a virus live in a bacterial cell, and used for typing of bacterial, it is specific and live in certain strain. There are two type of bacteriophage: Lytic bacteriophage: cause lysis of bacterial cell and used for typing 09/10/20 Dr.SS

10. Cont … Lysogenic bacteriophage: Does not cause lysis of bacterial cell but play important role in the gene transferring. There is a bacteriophage for any bacteria but usually used for typing of S. aurus in control of nosocomial infections. Phage typing also used for different epidemiological purpose as in Mycobacterium, Brucella, Salmonella...etc. 09/10/20 Dr.SS

11. Cont … Phage typing of S. aureus: There are 4 main group I, II, III and IV. And each group consist of different number of single phage. Method: Reconstitute the phage (activation the virus). Inoculate the NA plate with the tested organism after labelling. Add the phage as drop, incubate and read result 09/10/20 Dr.SS

12. Cont … Advantage: Very specific method. Disadvantage: Difficult to perform – need well equipped laboratory (preservation of virus) – time consuming – not used for all type of organisms. 09/10/20 Dr.SS

13. Phage typing of Salmonella typhimurium – is it still a useful tool for surveillance and outbreak investigation? Phage typing has for decades been useful as a phenotypical, definitive method for epidemiological characterisation of  Salmonella t yphimurium. The system recommended by the World Health Organization (WHO) Collaborative Centre for phage typing of  Salmonella  has, however, become rather complex, and the present study illustrates the challenges of sufficient standardisation of the interpretation of lysis results to make sure that the same strain is assigned to the same phage type in different laboratories. Even though molecular typing methods will replace phenotypic characterisation methods in the future, it is our opinion that phage typing will remain for some time a useful tool to strengthen global  Salmonella  surveillance. Therefore, improved standardisation and quality assurance is essential to obtain a robust and harmonised method that allows comparison of results between laboratories. 09/10/20 Dr.SS

14. Clarifications Questions to think [email protected] 09/10/20 Dr.SS

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