Multiple-locus variable-number tandem-repeat analysis as a tool for subtyping Listeria monocytogenes strains

Area of Science:

• Food safety microbiology
• Molecular epidemiology
• Bacterial strain typing

Background:

• Listeria monocytogenes outbreaks are challenging to detect due to low case numbers.
• Current pulsed-field gel electrophoresis (PFGE) methods for subtyping L. monocytogenes have interlaboratory variability issues.
• Accurate and reproducible subtyping is crucial for tracking foodborne pathogens.

Purpose of the Study:

• To develop and validate a novel multiple-locus variable-number tandem-repeat analysis (MLVA) method for L. monocytogenes.
• To create a robust and easily implementable subtyping protocol for PulseNet laboratories.
• To offer an alternative or complementary method to PFGE for L. monocytogenes strain identification.

Main Methods:

• Developed a novel MLVA method using eight loci multiplexed into two PCR reactions.
• Utilized capillary gel electrophoresis for high-throughput and accurate sizing of PCR products.
• Analyzed and clustered fragment sizes based on tandem repeat numbers.

Main Results:

• The developed MLVA method demonstrated strong epidemiological concordance when tested on 193 isolates.
• The technique proved to be rapid, inexpensive, and reliable for bacterial subtyping.
• MLVA showed high discriminatory power for differentiating L. monocytogenes strains.

Conclusions:

• The novel MLVA method is a suitable replacement or complement to PFGE for L. monocytogenes subtyping.
• This high-throughput method facilitates accurate interlaboratory comparisons in foodborne illness investigations.
• MLVA enhances the ability to track and control L. monocytogenes outbreaks effectively.