Detection, characterization and epidemiology of Shiga toxin-producing Escherichia coli in human infections

Shiga toxin-producing Escherichia coli (STEC) are foodborne pathogens that cause outbreaks and sporadic cases of gastroenteritis, and sometimes the life-threatening hemolytic uremic syndrome (HUS). The aims of this research were to evaluate STEC detection methods, to study Belgian hybrid E. coli pathotypes, to conduct an isolate-based risk assessment for HUS development, and to gain insight in the epidemiology of STEC infections in the UZ Brussel. Two rapid commercial assays were evaluated. The sensitivity of the SHIGA TOXIN QUIK CHEK enzyme immunoassay was too low to recommend direct fecal testing. The molecular multiplex BioFire FilmArray Gastrointestinal assay had a superior sensitivity, but misclassified certain pathogenic E. coli. Both assays could not detect Shiga toxin 2f (Stx2f). Two hybrid O104:H4 isolates were closely related to the German 2011 outbreak strain, and came from Belgian patients who traveled to the Mediterranean sea area. Belgian hybrid O80:H2 E. coli isolated from humans and calves were similar to the pathotype that is currently emerging in France, indicating a role for diarrheic calves in its transmission. The genes stx2, stx2a in particular, and eae were identified as significant risk determinants for HUS development. This lead to a new risk classification and virulence typing algorithm. STEC infections in the UZ Brussel were mainly sporadic, and a substantial portion of the patients was asymptomatic. As seen in other countries, Stx2f infection was quite prevalent and we reported the first Belgian STEC stx2f HUS case and stx2f positive E. albertii infection. The work presented in this PhD thesis emphasizes the importance of the culturing of samples for surveillance, outbreak detection, and identification of emerging hybrid E. coli pathotypes.