Purpose: Availability of a low-cost, yet capable MLVA platform could unlock the potential for wider use of this typing approach. We sought to evaluate the performance of a new multicolor capillary electrophoresis (CE) instrument (the MLVAnalyzer, Advanced Analytical Technologies, Ames, IA) for MLVA-based analysis of Salmonella. Specifically, we sought to evaluate the system’s discriminative ability and reproducibility using a panel of Salmonella strains.
Methods: Fluorescent dye-labeled primers (TAMRA, HEX, TET) targeting five variable number tandem repeat (VNTR) loci on the Salmonella genome were prepared and genomic DNA was extracted from various strains of Salmonella Typhimurium, Heidelberg and Enteritidis. Multiplex PCRs were performed, generating five differently-sized PCR products for each strain. Amplified fragments were separated by CE in the MLVAnalyzer and were analyzed by size and color using the system’s software.
Results: Multiplex PCR targeting short tandem repeats (STRs) yielded products ranging in size from ~150 to 500 bp. These were detected by the MLVAnalyzer as they passed in front of the system’s continuous linear filter using distance-phased color multiplexing and were differentiated using onboard software. The MLVAnalyzer provided accurate and reproducible differentiation of Salmonella strains, and its digital output facilitated database development and dendrogram-based analyses of Salmonella.
Significance: Our results indicate that the MLVAnalyzer can provide reliable strain typing data suitable for outbreak investigations and microbial source tracking. Availability of a lower-cost MLVA platform may help unlock the potential for wider use of MLVA by smaller laboratories as a capable alternative to PFGE.