Effective surveillance using multilocus variable number tandem repeat analysis and whole genome sequence analyses in enterohemorrhagic Escherichia coli O157.

Due to the potential of enterohemorrhagic Escherichia coli (EHEC) serogroup O157 to cause large foodborne outbreaks, national and international surveillance is necessary. For developing an effective method of molecular surveillance, conventional multilocus variable number tandem repeat analysis (MLVA) and whole genome sequencing (WGS) analysis were compared. WGS of 369 isolates of EHEC O157 belonging to seven major MLVA types and their relatives were subjected to comprehensive in silico typing, core genome (cg)SNP, and cgMLST analyses. The typing resolution was the highest in cgSNP analysis. However, determination of the sequence of the mismatch repair protein gene mutS is necessary because spontaneous deletion of the gene could lead to a hypermutator phenotype. MLVA had sufficient typing resolution for a short-term outbreak investigation and had advantages in rapidity and high throughput. cgMLST showed less typing resolution than cgSNP, but it is less time-consuming and does not require as much computer power. Therefore, cgMLST is suitable for comparisons using large datasets (e.g., international comparison using public databases). In conclusion, screening using MLVA followed by cgMLST and cgSNP analyses would provide the highest typing resolution and improve the accuracy and cost-effectiveness of EHEC surveillance. [ABSTRACT FROM AUTHOR]