A case of haemolytic uraemic syndrome (HUS) revealed an outbreak of Shiga toxin-2-producing O26:H11 infection in a nursery, with long-lasting shedders and person-to-person transmission, Italy 2015.

Shiga toxin-producing (STEC) represents a major issue for public health because of the severity of the associated illnesses, including haemolytic uraemic syndrome (HUS). In 2015, investigation of a case of HUS revealed an outbreak of Shiga toxin-2-producing O26 : H11 infection in a nursery in Italy. The investigation showed that the infection was transmitted to cases' contacts via person to person. The case finding was performed by testing for STEC stool samples of the HUS case's contacts within the family and the nursery. STEC O26 isolates were characterized by whole genome sequencing. Confirmed cases were repeatedly tested to monitor the duration of STEC shedding. Eleven STEC O26 cases were identified, including adults and asymptomatic patients. Clinical illness was only observed in children. Strain characterization revealed that a single clone harbouring the a and genes and the complete array of STEC-associated virulence genes, belonging to ST(21), was implicated in the outbreak. To reduce bacterial shedding, patients were treated with cefixime following clinical recovery. This antibiotic was well tolerated and did not induce any apparent consequences on patients' health. This study confirms that Stx2-producing O26 represents an emerging public health problem. The occurrence of outbreaks of infection by Stx2-producing O26 in nurseries is of particular concern, given the high probability of infection progressing in severity and resulting in secondary cases.