VARIANTS OF SHIGA-LIKE TOXIN-II CONSTITUTE A MAJOR TOXIN COMPONENT INESCHERICHIA-COLI O157 STRAINS FROM PATIENTS WITH HEMOLYTIC-UREMIC SYNDROME

The prevalence and genotype of Shiga-like toxins (SLTs) in Escherichia coil O157 strains from patients in Germany with haemolytic uraemic sy ndrome (HUS) were investigated. This was done by PCR amplification of the B-subunit genes with two primer pairs-one complementary to slt-IB, and the other homologous to both slt-IIB and slt-IIvB sequences. To d istinguish between sir-II and slt-IIv, the amplified DNA was digested with restriction endonucleases HaeIII and FokI, Of the 38 strains exam ined, 17 harboured sequences for slt-IIv; four contained only slt-IIv, three carried both slt-IIv and sit-I, and 10 strains had slt-IIv and sit-II. A further three genotypes (sit-I, sit-IT, sit-I/sit-II) were f ound in the remaining 21 strains resulting in a total of six sit genot ypes. To determine whether the sit genes were expressed, and whether g enotypes correlated with phenotypes, all strains were subjected to cyt otoxicity assays and colony ELISA. All 38 strains displayed cytotoxic activity to Vero cells in similar quantities. The SLT-I-specific monoc lonal antibody (MAb)13C4 reacted with all 10 strains in which sit-I se quences were identified. Colony blot ELISA with the SLT-II specific MA b11E10 detected 27 of 28 strains with sit-II sequences, but did not re act with any of the seven strains that carried sit-IIv, or sit-I and s lt-IIv. The high SLT variability shown here has diagnostic implication s and may well have consequences for the host response in infections a ssociated with these pathogens.