"FAMILY CLUSTER ASSOCIATED WITH SHIGA TOXIN-PRODUCING ESCHERICHIA COLI O26 SEROGROUP"

"Introduction: Shiga toxin-producing Escherichia coli (STEC) can cause severe human infections especially in the pediatric population who are at risk of progressing to life threatening systemic complications such as hemolytic uremic syndrome (HUS). In Romania, enhanced monitoring of STEC-associated HUS was implemented in year 2016 after a cluster of infections caused by STEC O26:H11 serotype heightened public awareness of their consequences. Objectives: This study describes the microbiological investigation initiated to identify a STEC-associated HUS pediatric case and determine additional infections among his household contacts. Methods: Fecal specimens collected from a small child hospitalized with HUS and his asymptomatic parents and brother were investigated using a culture-based approach which targeted STEC isolation, identification, and typing. PCR-based assays for key virulence genes (i.e., stx1 and stx2 types/subtypes, eae, and ehxA) were combined with traditional methods such as serogroup determination by slide agglutination. Also, multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) were used for strain genotyping. Results: STEC was identified only in the stool samples of the siblings, one who developed HUS and the other who remained asymptomatic. Both strains belonged to O26 E. coli serogroup and displayed an identical virulence gene profile (presence of stx2a, eae, and ehxA genes). Molecular typing by PFGE showed the STEC strains as highly related genetically and MLST assigned them to sequence type ST21 lineage. Conclusion: A family cluster of O26 STEC infections was detected by using a culture- based molecular approach. Further analysis at whole genome sequencing resolution level is needed for a detailed characterization of such pathogens of significant public health importance. Keywords: HUS, Shiga toxin-producing Escherichia coli, virulence genes, PCR, molecular typing"