Clinical presentation, complications and treatment of infection with verocytotoxin-producing Escherichia coli. Challenges for the clinician.

Seventeen years after its recognition, outbreaks and sporadic infections attributed to Escherichia coli O157 continue to increase. Acute gastrointestinal, and the systemic complications haemolytic uraemic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP), are frequent and severe. Current challenges that face clinicians are the early recognition of infection, identification of risk factors for poor prognosis, determination of appropriate monitoring for the development of complications, establishment of a therapeutic strategy and, finally, advice for patients about their long-term prognosis. Clinical features which, in combination, have been shown to distinguish E. coli O157 infection from other enteric pathogens are a history of bloody diarrhoea, visibly bloody stools, absence of fever, a leucocyte count greater than 10 x 10(9) l(-1) and abdominal tenderness on physical examination. The most consistent risk factors for the development of HUS/TTP are the extremes of age and a raised leucocyte count. Bloody diarrhoea and 'antimotility' drugs are also likely to be important risk factors. Recent evidence from the central Scotland outbreak suggests that individuals who are taking drugs that reduce gastric acidity or antibiotics at the time of infection with E. coli O157, or who have a short incubation period, may also be at increased risk of progression to HUS/TTP. Clinical management, in particular the role of antibiotics in gastrointestinal infection, remains controversial, and retrospective assessment of the 1996 outbreaks from central Scotland and Japan only adds to this controversy. Therapeutic plasma exchange is a promising treatment for adults who develop HUS/TTP, but its role has yet to be determined definitively, either in a randomized controlled trial or by an international register of cases. Significant chronic sequelae of infection occur, particularly irritable bowel syndrome after uncomplicated gastrointestinal infection, and renal failure after HUS/TTP. Their frequency and severity are likely to become evident over the next decade.