Serogroups and Toxin Variants of Clinical Shiga Toxin-Producing Escherichia coli Strains Isolated from Patients with Hemolytic Uremic Syndrome in Turkey.

Shiga toxin-producing Escherichia coli (STEC) refers to a group of bacteria that can cause infections, which are common worldwide and pose a serious public health problem, as they can lead to conditions such as hemorrhagic colitis and hemolytic uremic syndrome (HUS). HUS is a disease characterized by microangiopathic hemolytic anemia, thrombocytopenia, and renal failure. Determination of serogroups and toxin profiles of STEC is important for estimating their disease-causing potential and predicting epidemiological changes. This study analyzed STEC isolates from 46 pediatric HUS patients across Turkey, using polymerase chain reaction to determine O serogroups and Shiga toxin (Stx) variants from stool samples collected between 2016 and 2019. Of the patients, 25 (54.3%) were in the 0-2 age group. Of the isolates, 82.6% were non-O157 serogroup. The most detected serogroup was O145 (32.6%), and 28.3% of the serogroups were not typed. Of the strains, 8 (17.4%) had Stx1 alone, 26 (56.5%) had Stx2 alone, and 12 (26.1%) had both Stx1 and Stx2. The Stx variants occurred in seven combinations, with the most common being Stx2a alone (56.5%). The duration of hospitalization for patients with Stx2a was found to be longer than that for patients with other variants (p = 0.01). This study highlights a concerning trend in Turkey, where non-O157 serogroups, particularly O145, emerged as prevalent causes of HUS. The predominance of Stx2a among our isolates and the longer hospitalization duration for patients with Stx2a support findings linking this variant to severe clinical outcomes, including HUS. Understanding the dynamics of these Stx variants will help better prepare for and mitigate the impacts of STEC infections in our population.