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A phage typing system for Salmonella infantis
V G László1, K Csák, E S Csórián
1National Institute of Hygiene, Budapest, Hungary.
Abstract:
A phage typing method applying 9 type phages was elaborated to subdivide Salmonella infantis. Results are reported by the use of Farmer's mnemonic. Out of 4847 S. infantis strains, 4602 were of human and 245 of non-human origin. The strains were typable in 98.9%. Two phage types occurred more frequently than 20%, four phage types between 5 and 10%, seven phage types less than 5%, and twenty-eight phage types less than 1%. The strains originated from outbreaks in 28.7% and from sporadic cases in 71.3%. A total of 1320 strains examined for phage type was isolated from 4 field epidemics, 39 community outbreaks and 370 family infections. In the second version of the method two phages were substituted by two more effective ones. The phage typing method was suitable for epidemiological purposes. Inducing in vitro changes in phage types by lysogenization and plasmid acquisition, phage types 111, 113, 311, 313 and 343 changed to phage types 213, 243, 513 and 543 after lysogenization and phage types 311 and 543 to phage types 548, 565 and 885 due to plasmid acquisition.
Insights
A novel phage typing method effectively subdivides Salmonella infantis strains, aiding in epidemiological investigations. This technique enhances the ability to track bacterial sources and transmission routes in public health settings.
Area of Science:
- Microbiology
- Epidemiology
- Molecular Biology
Background:
- Salmonella infantis is a significant pathogen.
- Accurate subtyping is crucial for epidemiological surveillance.
- Existing phage typing methods may require refinement.
Purpose of the Study:
- To develop and validate a refined phage typing method for Salmonella infantis.
- To assess the epidemiological utility of the new method.
- To investigate mechanisms of phage type variation.
Main Methods:
- A 9-phage typing scheme was developed for Salmonella infantis.
- 4847 strains of human and non-human origin were analyzed.
- Phage type changes were induced in vitro via lysogenization and plasmid acquisition.
Main Results:
- The method achieved 98.9% typability for Salmonella infantis strains.
- Specific phage types exhibited varying frequencies, with some dominating.
- The method successfully differentiated strains from outbreaks and sporadic cases.
- In vitro experiments demonstrated phage type alterations through genetic modifications.
Conclusions:
- The elaborated phage typing method is highly effective for subdividing Salmonella infantis.
- The method is suitable for epidemiological purposes, aiding in outbreak investigations.
- Lysogenization and plasmid acquisition can induce in vitro changes in Salmonella infantis phage types.