Listeria environmental sampling tests are compatible with polymorphic locus sequence typing

Area of Science:

• Food safety microbiology
• Molecular diagnostics
• Pathogen surveillance

Background:

• Food processors utilize environmental sampling tests (ESTs) for pathogen detection, particularly Listeria monocytogenes.
• Current ESTs offer convenience, speed, and cost-effectiveness for presumptive pathogen identification.

Purpose of the Study:

• To evaluate the feasibility of integrating polymorphic locus sequence typing (PLST) with common Listeria environmental sampling tests (ESTs).
• To determine if PLST can provide valuable strain typing data for Listeria monocytogenes tracking and source identification.

Main Methods:

• Five commercial Listeria ESTs (broth and gel-based) were inoculated with Listeria monocytogenes and Listeria innocua strains.
• Heat treatment inactivated bacteria, followed by DNA preparation for PCR amplification of PLST loci (LmiMT1 and LisMT2).
• PCR products were Sanger sequenced, and phylogenetic analysis was performed.

Main Results:

• All inoculated ESTs yielded single, clear PCR products for PLST analysis.
• Sanger sequencing produced high-quality chromatograms, enabling accurate phylogenetic analysis.
• Phylogenetic analysis confirmed bacterial identities and revealed strain relatedness to database sequences.

Conclusions:

• Polymorphic locus sequence typing (PLST) is compatible with multiple environmental sampling tests (ESTs) for Listeria.
• Integrating PLST enhances ESTs by providing crucial strain-level data for improved pathogen surveillance and control in food processing environments.