Abstract
The clinical spectrum following infection with Shiga toxin-producing Escherichia coli (STEC) is wide ranging and includes hemorrhagic colitis and life-threatening hemolytic uremic syndrome (HUS). Severity of STEC illness depends on patients' age and strongly on the infecting strains' virulence. Serogroup O157 is often assumed to be more virulent than others. Age-adjusted population-based data supporting this view are lacking thus far.We conducted a large retrospective cohort study among patients of community-acquired gastroenteritis or HUS diagnosed with STEC infection, reported in Germany January 2004 through December 2011. Age-adjusted risks for reported hospitalization and death, as proxies for disease severity, were estimated for STEC serogroups separately, and compared with STEC O157 (reference group) using Poisson regression models with robust error estimation.A total of 8,400 case-patients were included in the analysis; for 2,454 (29%) and 30 (0.4%) hospitalization and death was reported, respectively. Highest risks for hospitalization, adjusted for age and region of residence, were estimated for STEC O104 (68%; risk ratio [RR], 1.33; 95% confidence interval [CI], 1.19–1.45), followed by STEC O157 (46%). Hospitalization risks for the most prevalent non-O157 serogroups (O26, O103, O91, O145, O128, O111) were consistently and markedly lower than for O157, with the highest RR for O145 (0.54; 95% CI, 0.41–0.70) and the lowest for O103 (0.27; 95% CI, 0.20–0.35). Mortality risk of O104 was similar to O157 (1.2% each), but the group of all other non-O157 STEC had only 1/10 the risk (RR, 0.09; 95% CI, 0.02–0.32) compared to O157.The study provides population-based and age-adjusted evidence for the exceptional high virulence of STEC O157 in relation to non-O157 STEC other than O104. Timely diagnosis and surveillance of STEC infections should prioritize HUS-associated E. coli, of which STEC O157 is the most important serogroup.
Highlights
Shiga toxin-producing Escherichia coli (STEC) are a heterogeneous group of organisms [1,2,3] and the clinical spectrum caused by gastrointestinal infection with STEC varies widely [4,5]
The risk of hospitalization for case-patients infected by STEC O104 was 33% higher than that of STEC O157 (RR, 1.33; confidence intervals (CI), 1.19–1.45)
Case-patients infected by STEC O104, all part of one large outbreak in 2011, had a 1/3 higher risk of hospitalization and a comparable risk of dying than those infected by O157, according to German surveillance data
Summary
Shiga toxin-producing Escherichia coli (STEC) are a heterogeneous group of organisms [1,2,3] and the clinical spectrum caused by gastrointestinal infection with STEC varies widely [4,5] Besides asymptomatic infection it includes acute non-bloody diarrheal illnesses, and hemorrhagic colitis and the hemolytic uremic syndrome (HUS), a life-threatening thrombotic microangiopathy leading to acute renal dysfunction approximately one week after onset of diarrhea. The historically rooted distinction between (sorbitol-nonfermenting) STEC O157 and (sorbitol-fermenting) non-O157 STEC is still widely upheld [19] This is probably due to these differences in diagnosis and the notion - supported by several studies - that STEC O157, on average, is more virulent than many if not all other STEC serogroups [20,21], and is outbreak-prone [22]. None of the sparse population-based comparisons between STEC serogroups has accounted analytically for the possible confounding effect of patients’ age
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