Harmonization of the multiple-locus variable-number tandem repeat analysis method between Denmark and Norway for typing Salmonella Typhimurium isolates and closer examination of the VNTR loci

Abstract

Aims: Harmonization and evaluation of the multiple‐locus variable‐number tandem repeat analysis (MLVA) method for sub‐typing Salmonella enterica ssp. enterica serovar Typhimurium (Salm. Typhimurium) in Denmark and Norway, and analysis of the typing data. Methods and Results: The Salm. Typhimurium MLVA (STMLVA) method, which uses length polymorphisms in five tandem‐repeated DNA loci to differentiate isolates, was harmonized between Denmark and Norway, using a common set of 14 isolates. The MLVA assay that is routinely used at the Norwegian Institute of Public Health was set up at the Statens Serums Institute. Both the institutes used an ABI‐310 Genetic Analyzer for capillary separation of PCR products, and the same internal size standard. Running the same set of 14 test isolates in both countries and comparing the results showed an excellent typing match at all loci in all isolates. Subsequently, 461 isolates were genotyped in Norway and 454 isolates were genotyped in Denmark. The STMLVA assay displayed a large number of allelic profiles that were distinct for each country as well as shared profiles. Differences in variable number of tandem repeats allele frequencies and absence of amplification products were observed between Denmark and Norway. Conclusions: The MLVA method was set up in two different laboratories and produced completely matching typing data that could be shared rapidly by e‐mail for comparison. Notably, differences in allele frequencies and absence of amplification were noted between the countries. Significance and Impact of the Study: The STMLVA method was shown to be easily implemented and to produce typing data, which were shared over the Internet. This enables increased speed of typing and comparison of data between countries, when compared with earlier typing methods. Information embedded in the allele frequencies might give clues to the origin and source of isolates.

Plasmid-mediated Quinolone Resistance inSalmonella enterica, United Kingdom

“…Twenty-one qnrS1-positive S. Typhimurium were subtyped by variable number tandem repeat (VNTR) analysis to determine whether the increase was caused by spread of >1 distinct strains (7). Twenty isolates produced 1 of 3 related profi les (loci of VNTR profi les are ordered STTR9-STTR5-STTR6-STTR10pl-STTR3): 1-4-0-0-3, 9 isolates; 1-5-0-0-3, 3 isolates; or 1-6-0-0-3, 8 isolates.…”

Novel Virulence Gene and Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR) Multilocus Sequence Typing Scheme for Subtyping of the Major Serovars of Salmonella enterica subsp. enterica

“…Several nucleic acid-based molecular subtyping methods have been used to subtype Salmonella, including amplified fragment length polymorphism (AFLP) (18,32,36,42,46), multiple-locus variable-number tandem-repeat analysis (MLVA) (2,30,31,37), and pulsed-field gel electrophoresis (PFGE) (35). PFGE is currently considered the "gold standard" method for subtyping food-borne pathogens and is the subtyping method used by PulseNet, the molecular surveillance network in the United States and throughout the world to investigate food-borne illnesses and outbreaks (17).…”

The biochemical and molecular characteristics of Streptococcus equi subsp. zooepidemicus isolated from the genital tract of Thoroughbred mares in Korea

“…If a SzP and ISR were not detected during fragment analysis, reactions were repeated by using singleplex reactions with minor modifications to amplify the specific locus. In that particular instance, the primer concentration was increased to 0.2 μmole/ml, annealing temperatures were reduced to 49 o C, and the extension time was tripled to amplify larger fragments because of possible insertion sequence element transposition or other genetic events (Lee and Cho, 2006;Lindstedt et al, 2007;Hirota et al, 2010;HyytiaTrees et al, 2010). After fragment analysis, corresponding peak data were examined by using GeneMapper Ver.…”