STEC-associated hemolytic uremic syndrome (HUS) is rarer in adults than children but causes more severe disease and death in older people, according to a study.

Researchers looked at HUS caused by Shiga toxin-producing E. coli (STEC) in 96 adults in France during 2009 to 2017. A total of 69 of the patients had underlying health conditions. HUS is a severe complication associated with E. coli infections that causes kidney failure.

In total, 61 patients required dialysis, 50 had a serious neurologic complication, 34 required mechanical ventilation, and 19 died during hospitalization. Patients died three to 152 days after admission and had a median follow-up period of 112 days.

Findings emphasize that, in adults, STEC-associated HUS is a severe disease that can cause multiple organ failure, according to the study published in Emerging Infectious Diseases.

Surveillance situation
Most patients included in the study who died had STEC strains belonging to non-O104 and non-O157 serogroups. The top serogroups in infected people were O91 and O157. STEC isolates from urine samples belonged to the O104, O91, O106, O126, O174, and O148 serogroups and isolates from blood samples included the O80, O103, and O128 serogroups.

French national health authorities do not have a dedicated surveillance system for STEC-associated HUS in adults. Surveillance for STEC-associated HUS in children under 15 years of age started in 1996.

During the study period, 1,095 STEC-associated HUS cases in children were reported to Santé Publique France (the public health agency) through the country’s pediatric surveillance network. In 2019, 168 cases of pediatric HUS were reported to the agency, which is the most since officials started keeping records.

Severity of the disease, a probable underestimated prevalence, and the risk for outbreaks of emerging STEC-associated HUS provide strong arguments for active epidemiological and microbiological surveillance, according to the study.

Despite the much lower incidence of HUS among adults than children, most deaths caused by STEC-associated HUS are in people older than 60 years of age.

Death risk factors
Researchers found that 20 percent of adults who had STEC-associated HUS died during hospitalization but less than 1 percent of children who had this illness died in France during 2007 to 2016.

The risk of death from STEC-associated HUS increases for people above the age of 40. Prevalence of antibodies against Shiga toxin decreases for those older than 40, which might explain the more severe forms of STEC-associated HUS in elderly people.

Scientists found a strong association between underlying conditions and decreased survival, especially for patients with immunodeficiency.

As cases of STEC-associated HUS in adults remain rare, clinical characteristics and effects of therapeutic strategies on outcome are uncertain. Patients were treated mainly with best supportive care, therapeutic plasma exchange, or eculizumab. In total, 26 people were treated with macrolides.

Previous studies suggest the use of antimicrobial drugs during early stages of STEC infection is associated with development of HUS. However, the effects of using such drugs after HUS diagnosis is unknown. Researchers found the prescription of multiple antimicrobial drugs was common, especially in cases of severe infection.