Dirk Werber aEmail Address, Martina Bielaszewska b, Christina Frank a, Klaus Stark a, Helge Karch b

Hugh Pennington’s thorough review (Oct 23, p 1428)1 focuses on classic (ie, non-sorbitol-fermenting) enterohaemorrhagic Escherichia coli O157:H7, the main cause of haemolytic uraemic syndrome (HUS) worldwide. However, its phylogenetically close relative, sorbitol-fermenting E coli O157:NM (non-motile), warrants note.

Sorbitol-fermenting E coli O157 accounts for 17% of sporadic cases of HUS2 and caused seven outbreaks in Germany between 1988 and 2009, the largest of which involved 38 cases of HUS.3 A large outbreak also occurred recently in the UK.4 Several features distinguish sorbitol-fermenting E coli O157 from its prominent cousin, E coli O157:H7. First, outbreaks caused by sorbitol-fermenting O157 strains are dominated by children with HUS who require more sessions of haemodialysis and have a higher risk of dying (case-fatality 11%) than do HUS patients infected with E coli O157:H7.3, 5

Second, culture-based methods that make use of selective and differential media will not detect sorbitol-fermenting E coli O157.5 Targeting of the sfp gene cluster (encoding Sfp fimbriae) as a marker can reliably screen for sorbitol-fermenting E coli O157, but is seldom applied even in specialised laboratories, resulting in underdiagnosis of this pathogen.

Third, the reservoir and exposure routes of sorbitol-fermenting E coli O157 are still unknown, but they are likely to be different from those of E coli O157:H7. Consequently, existing prevention guidelines for E coli O157 might not be appropriate for sorbitol-fermenting E coli O157—a pathogen with probably greater virulence.

Because no specific treatment is available for HUS, prevention is pivotal. Further epidemiological investigations on reservoirs and risk factors for sorbitol-fermenting E coli O157 infections are needed, which will require timely identification of cases. Therefore, we recommend sfp testing of stool specimens in all children with HUS, in addition to screening for E coli O157:H7 on sorbitol MacConkey agar.

We declare that we have no conflicts of interest.

References

1 Pennington H. Escherichia coli O157. Lancet 2010; 376: 1428-1435. Summary | Full Text | PDF(316KB) | CrossRef | PubMed

2 Bielaszewska M, Kock R, Friedrich AW, et al. Shiga toxin-mediated hemolytic uremic syndrome: time to change the diagnostic paradigm?. PLoS One 2007; 2: e1024. CrossRef | PubMed

3 Alpers K, Werber D, Frank C, et al. Sorbitol-fermenting enterohaemorrhagic Escherichia coli O157:H- causes another outbreak of haemolytic uraemic syndrome in children. Epidemiol Infect 2009; 137: 389-395. CrossRef | PubMed

4 Pollock KG, Locking ME, Beattie TJ, et al. Sorbitol-fermenting Escherichia coli O157, Scotland. Emerg Infect Dis 2010; 16: 881-882. PubMed

5 Ammon A, Petersen LR, Karch H. A large outbreak of hemolytic uremic syndrome caused by an unusual sorbitol-fermenting strain of Escherichia coli O157:H. J Infect Dis 1999; 179: 1274-1277. CrossRef | PubMed

a Robert Koch Institute, Department for Infectious Disease Epidemiology, 13086 Berlin, Germany

b Institute of Hygiene and National Consulting Laboratory on Hemolytic Uremic Syndrome, University of Münster, Münster, Germany