Detection of virulent XXXX O157 strains using multiplex PCR and single base sequencing for SNP characterization.

@entity1 @entity23345 @entity72688 @entity2775 @entity10952 @entity2142 @entity526
AIMS: To compare 167 Norwegian @entity1 and nonhuman @entity526 O157:H7/NM (nonmotile) isolates with respect to an @entity2775 single nucleotide polymorphism (SNP) in the tir gene and to detect specific SNPs that differentiate STEC O157 into distinct virulence clades (1-3 and 8). METHODS AND RESULTS: We developed a multiplex PCR followed by single base sequencing for detection of the SNPs, and examined the association among SNP genotype, virulence profile (stx and eae status), multilocus variable number of tandem repeats analysis (MLVA) profile and clinical outcome. We found an over-representation of the T allele among @entity1 strains compared to nonhuman strains, including 5/6 @entity2142 cases. Fourteen strains belonged to clade 8, followed by two clade 2 strains. No clade 1 nor 3 isolates were observed. @entity10952 in combination with either @entity23345 (EDL933) or @entity23345 were frequently observed among @entity1 strains, whereas @entity23345 was dominating in nonhuman strains. MLVA indicated that only single cases or small outbreaks with @entity526 O157 have been observed in Norway through the years 1993-2008. CONCLUSION: We observed that the tir @entity72688 SNP and the stx status were different between @entity1 and nonhuman O157 strains. No major outbreaks were observed, and only a few strains were differentiated into the virulence clades 2 and 8. SIGNIFICANCE AND IMPACT OF THE STUDY: The detection of virulence clade-specific SNPs enables the rapid designation of virulent @entity526 O157 strains, especially in outbreak situations.
