Downloaded from www.microbiologyresearch.org by IP: 54.70.40.11 On: Sat, 03 Nov 2018 12:37:32 J. Med. Microbiol. - Vol. 47 (1998), 1039-1045 0 1998 The Pathological Society of Great Britain and Ireland REV1 EW ARTICLE New perspectives on the role of Escherichia coli 0157:H7 and other enterohaemorrhagic E. coli serotypes in human disease P. N. GOLDWATER and K. A. BETTELHEIM* Microbiology and infectious Diseases Department, Women’s and Children’s Hospital, North Adelaide, South Australia 5006 and *National Escherichia coli Reference Laboratory, Victorian infectious Diseases Reference Laboratory, Fa irfie id, Victoria, A us tra lia This review compares the rates of detection of non-O157:H7 enterohaemorrhagic Escherichia coli (EHEC) with EHEC 0157:H7 in outbreaks and sporadic cases of human disease by analysing Australian data and the world literature. Numerous outbreaks of disease have been attributed to EHEC 0157:H7. In many studies, isolation rates of this organism have been low and attempts to seek other EHEC have not been made. Ease of isolation and identification of the 0157:H7 serotype may have given the impression that this serotype was the sole organism responsible for the outbreaks. Careful review and analysis shows that serotypes other than 0157:H7 also play an important role in human disease. Evidence is presented from several overseas outbreaks described in the literature, as well as from investigations of the Adelaide 0 l l l : H - outbreak, that suggests an association between severity of disease and multiple infecting serotypes. While not diminishing the role of the 0157:H7/H- clone, this review indicates that other serotypes can be responsible for outbreaks as well as cases of sporadic human disease. The current focus on 0157:H7 has major implications in terms of diagnosis, the food industry and human Introduction From the first description 15 years ago [I] of outbreaks of disease caused by enterohaemorrhagic Escherichia coli (EHEC) 0157:H7, this serotype has tended to dominate the world literature on EHEC. Evidence suggests that EHEC 0157:H7 isolates are derived from one particularly successful clone of E. coli that has spread around the world. Long before the emergence of this strain, and ever since, there have been reports of human cases and outbreaks of disease caused by serotypes of E. coli other than 0157:H7. On occasion, these may occur concomitantly with 0 157:H7 cases, which may lead to the false labelling of an outbreak as one caused by this serotype only. Investigation of the Adelaide haemolytic uraemic syndrome (HUS) outbreak has provided several in- sights into the epidemiology of EHEC. Polymerase chain reaction (PCR) detection of E. coli stx genes Received 19 Dec. 1997; revised version received 19 May 1998; accepted 26 May 1998. Corresponding author: Dr I? N. Goldwater. health. had been introduced as part of research into sudden infant death syndrome. It was fortuitous that the PCR assay was available at the time of the epidemic as it allowed detection of EHEC 0 1 11:H-. The hospital laboratory had not introduced selective media for the isolation of E. coli 0157:H7, but such an approach, without PCR detection of stx genes, would have failed to detect E. coli Olll:H-. The examination in a different laboratory of a faecal specimen from one of the Adelaide HUS cases who was hospitalised interstate, and the detection in that specimen of a number of EHEC serogroups including 0111 and 0157, alerted the epidemic investigation to the simultaneous presence of the 0 157 clone, which was found subsequently in two other patients [2]. Exam- ination of reports of outbreaks of EHEC-related disease indicates that most have been under-investi- gated from the point of view of the possible involvement of multiple serotypes of E. coli. This review provides a fresh look at the epidemiology of E. coli and raises issues important to our understanding of why some epidemics are mild clinically and others severe. In addition, the review illustrates some of the important issues involved in the microbiology of food- borne E. coli disease.