Phage Typing-Identification of prokaryotes

1. Phage Typing
Dr. Mabel Merlen Jacob
Assistant Professor
Department of Microbiology
St. Mary’s College
Thrissur-680020
Kerala

2. Phage Typing,Dr.Mabel Merlen Jacob, St.Mary’s College
Identification of prokaryotes
•Identification of prokaryotes using phenotypic characteristics
• Identification of prokaryotes using genotypic characteristics
• Characterizing strain differences

3. Phage Typing,Dr.Mabel Merlen Jacob, St.Mary’s College

4. Phage Typing,Dr.Mabel Merlen Jacob,St.Mary’s College
 Distinguish among different stains of bacteria -Especially when
only certain strains cause disease.
(Only certain strains of E. coli cause intestinal disease-
presence of virulence factors such as toxin production etc.)
 Detecting strains differences - helpful in tracing source of an
outbreak.
Characterizing strain differences

5. Phage Typing,Dr.Mabel Merlen Jacob,St.Mary’s College

6. Phage Typing,Dr.Mabel Merlen Jacob,St.Mary’s College
Phage Typing
 Strains of a given species sometimes differ in their susceptibility to
various types of bacteriophages.
 The zone of clearing around the bacteriophage spot indicate the
susceptibility patterns of the test organism to different phages.
 Different patterns compared to determine strain differences

7. Phage Typing,Dr.Mabel Merlen Jacob,St.Mary’s College

8. Phage Typing,Dr.Mabel Merlen Jacob,St.Mary’s College
Phage may be very specific
-infect only a few strains of a certain bacterial species
or
strains of two or more species of a particular genus-
http://microamaze.blogspot.com/2015/11/phage-typing-of-salmonella-typhimurium.html

9. Phage Typing,Dr.Mabel Merlen Jacob,St.Mary’s College
 Phage typing - characterizing and detecting bacterial strains by their
reaction (susceptibility/ resistance) to various known strains of
phages.
 employed in epidemiology to identify an infectious agent.
 eg; 1) strains of Staphylococcus aureus/ Listeria involved in
outbreaks of food poisoning or other infections.
2) identification of Bacillus anthracis, the causative agent of
anthrax

10. Phage Typing,Dr.Mabel Merlen Jacob,St.Mary’s College
 sterile, fairly dried agar plates pre-inoculated with the phage
suspensions -up to 25 phage preparations using a multi-syringe
applicator
 agar surface flooded with broth culture of the Listeria strains;
observed after overnight incubation
 The phage particles do not diffuse along the agar surface; remain in
the circular area coincident with the original phage drop.
Reversed phage typing procedure – Listeria

11. Phage Typing,Dr.Mabel Merlen Jacob,St.Mary’s College
 prepared plates can be used directly or stored at 4°C until use
(two weeks)
 More than 100 ready-to-use phage typing plates from 1 ml of
each of the phage suspensions
 prepared, ready-to-use typing plates – no need of cloning and
titration of phages in each laboratory.
 a two-fold increase in efficiency than the conventional method.

12. Phage Typing,Dr.Mabel Merlen Jacob,St.Mary’s College
 Specificity of the phage employed
 Medium used for testing lytic activity of phage
 opaque media containing egg/ dense materials
to be avoided – visualization of plaques difficult.
 Media should have no inhibitory action on growth of
host bacterium
 on adsorption of phage
eg; Tween 80, malachite green – mycophages, presence of
bacteriocins or other inhibitory substances and/or proteins liberated by
the lysed host cells.
Important Considerations

13. Phage Typing,Dr.Mabel Merlen Jacob,St.Mary’s College