Multiple-Locus Variable-Number Tandem Repeat Analysis Scheme for Non-O157 Shiga Toxin-Producing Escherichia coli: Focus on Serogroups O103, O121, O145, O165, and O91.

Non-O157 Shiga toxin-producing Escherichia coli (STEC) infections are a growing concern for public health. The number of sporadic cases and outbreaks of non-O157 STEC infections have increased in recent years. Molecular subtyping is an essential tool that allows high-resolution and rapid differentiation of isolates, identification of case clusters, and detection of outbreak clusters. Multiple-locus variable-number tandem repeat analysis (MLVA) is one of the most useful typing methods for differentiating isolates that cause foodborne diseases. In Japan, serogroups O26, O111, O103, O121, O145, O165, and O91 have been frequently isolated or associated with severe cases of non-O157 STEC infections. In this study, we designed an MLVA scheme (MLVA43) for serogroups O103, O121, O145, O165, and O91 by adding 26 new loci to an MLVA scheme (MLVA17) previously developed by our group for serogroups O157, O26, and O111 using 17 loci. We found that the discriminatory power of MLVA43 was comparable to that of pulsed-field gel electrophoresis (PFGE) for serogroups O103, O145, O165, and O91, and superior to that of PFGE for O121. MLVA43 identified more profiles than did MLVA17, except for serogroup O111 with 707 isolates. The MLVA43 scheme will enable rapid detection of outbreak clusters, which will aid in implementing rapid control measures against non-O157 STEC infections.