To date, many studies have reported identifying risk factors for the progression of STEC infection to HUS. Young age, female sex, STEC serotype encoding only Shiga toxin 2, and use of antibiotics are reported as risk factors for progression to HUS [1]. A protective effect of probiotics, frequently prescribed, has been assumed [2].

It is well known that maternal breastfeeding (BF) is associated with lower incidence of acute infectious gastroenteritis conditioning the composition of the gastroenteric microbiota [3]. This consideration led us to surmise a hypothesized protective role of BF in the clinical evolution of typical HUS (STEC-HUS) in a cohort of 96 children (44 M, 52 F) admitted to our hospital from January 2012 to September 2023.

The single-center, retrospective study involved conducting a telephone interview with the patients’ mothers to learn about the mode and duration of milk feeding during the first year of life. The patients were then divided into two groups: BF (breastfed) and FF (formula-fed).

The BF group consisted of 65 boys (67.7%) and the FF group of 29 boys (30.2%), after the exclusion of two girls who died on the first day of hospitalization. In the BF group, this exclusive milk feeding mode which was continued for 6 months in 23 patients and between 6 and 12 months in 24 patients, and in 12 patients, BF was extended for over 12 months. In this group, we identified a subgroup, called BF6, of 17 children, in which the onset of HUS occurred within 6 months after the end of BF.

For each patient, information on the HUS course was evaluated regarding (1) need for blood transfusion; (2) need and duration of dialysis and/or plasmapheresis; (3) kidney and extrarenal involvement (neurological, gastroenteric); and (4) kidney and extrarenal sequelae. Each variable was evaluated in the two groups (Table 1).

Table 1 Summary and comparative data between BF (breastfeeding) and FF (formula-fed) groups
Full size table

There were no statistically significant differences between the BF and FF groups in relation to the need for blood transfusion or in relation to the need for dialysis or plasmapheresis and in the occurrence of extrarenal complications.

In conclusion, our study, although limited by the small size of the sample examined, excludes a protective role by BF on STEC-HUS course.

However, in our territory, a surveillance protocol for bloody diarrhea has been activated [4], which recognized, in the period 06/2018 to 30/11/2022, out of a total of 2409 cases, 201 STEC infections (8.34%). Of these, only 9.9% evolved toward HUS, but it is not known what the mechanisms are that determine this evolution. This suggests the continuation of the study to verify whether the hypothesized but not demonstrated protective role of BF on the course of HUS can rather be realized in the non-evolution to HUS of subjects with STEC infection.