Phage typing study

Phage typing bacterial typing method based on a strain's susceptibility to a set of specific bacteriophages . Each phage, or bacterial virus, selectively infects certain bacterial strains, resulting in a unique susceptibility fingerprint specific to each isolate.

This technique is used to differentiate strains belonging to the same bacterial species , identify cross-contaminations and trace the origin of contaminations in industrial, agri-food, environmental or pharmaceutical environments.

Phage typing represents a powerful microbiological traceability tool , particularly for monitoring persistent contamination in production lines, industrial surfaces or finished products.

Methods and protocols used

Phage typing relies on the specific interaction between bacteriophages and host bacteria .

Main steps of the analysis:

1. Culture of the typing bacterial strain on nutrient medium.
2. Application of different specific bacteriophages onto the bacterial surface.
3. Observation of lysis patches (clear areas formed by bacterial destruction by the phage).
4. Establishing the sensitivity profile of the strain to each phage tested.
5. Comparison with reference profiles to identify or differentiate the strain.

Modern methods combine classical phage typing with molecular tools such as:

• PCR of strains or phages.
• sequencing (NGS) for detailed characterization of bacterial and phage genomes.
• Bioinformatic analysis for phylogenetic classification and comparison between isolated strains.

Matrices involved

Phage typing is applied to many matrices:

• Agri-food products : milk, meat, fermented products, ready-to-eat foods.
• Industrial areas : production lines, tanks, packaging, equipment.
• Water and effluents : environmental microbiological control.
• Bioproducts and probiotic formulations : verification of the purity and stability of strains.
• Materials and packaging : investigation of bacterial contamination related to packaging.

Industrial and regulatory applications

Phage typing is particularly used for:

• Tracing cross-contamination within a production site.
• Identify the source of a recurring contamination (e.g. Listeria monocytogenes , Staphylococcus aureus , Salmonella enterica ).
• Monitor the effectiveness of cleaning and disinfection protocols.
• Ensuring the microbiological conformity of finished products.
• Establishing a bacterial risk profile as part of a quality audit or regulatory assessment.

microbiological surface control and next-generation sequencing (NGS) approaches .

Related analyses

For an integrated approach to microbiological safety, YesWeLab recommends combining phage typing with other complementary analyses:

• Analysis of gene expression to link phage sensitivity profiles to the genetic activity of strains.
• Study of alpha and beta diversity to characterize the overall microbial composition.
• Sterility test to verify the absence of microbial contamination in finished products.
• Ecotoxicological test (Microtox) to assess the biological effects of contamination.

YesWeLab's expertise

YesWeLab relies on a network of ISO 17025 and COFRAC accredited laboratories , specializing in industrial microbiology and molecular biology .

Thanks to the YesWeLab digital platform , it is possible to:

• Order and track your analyses online,
• Centralize your microbiological data,
• Access comprehensive and comparative reports,
• Benefit from personalized scientific support.