Escherichia coil 'O' group serology of a haemolytic uraemic syndrome (HUS)epidemic

This is the first comprehensive serological analysis of a haemolytic uraemi c syndrome (HUS) outbreak. A wide range of 'O' group Escherichia coli antib ody responses in patients and controls was examined. The study provides a u nique insight into the epidemiology of such epidemics, points a map to the most appropriate investigation of these and indicates possible answers to a number of issues related to severity of disease. In order to be able to te st for a wide variety of E. coil 'O' antigens, a microagglutination assay E as used to examine E. coli 'O' group serological responses of 22 children admitted to hospital with HUS and 14 contemporaneous age-matched controls. A total of 51 'O' serogroup strains were used. These included 'O' groups re ported to be associated with cases of HUS, with 6 isolates from patients as sociated with the Adelaide outbreak (O26, O111, O123 and O157), environment al Verocytotosigenic/Shiga-toxin producing Escherichia coli (VTEC/STEC) str ains and common human commensal strains. Sixteen clinically confirmed HUS c ases (72.7%) of 22 seroconverted to 1 or more serogroups of which 11 (50%) seroconverted to O111 (the serogroup isolated from 16 patients). In additio n, 11 (50%) and 10 (45.5%) developed antibody to O137 and O135, respectivel y, although no stool isolates of these serogroups mere made. Seventeen (77. 3%) of 22 HUS patients had antibody to serogroup O157, with 11 (50%) seroco nversions, however, O157:H-ras isolated from only 2 of these. Overall, titr es ranged from 100 to 6400, some of the highest in 3 patients were against O157, whose faeces yielded only Enterohaemorrhagic E. coli (EHEC) O111, and only 1 developed O111 antibody. Mixed infection was demonstrated serologic ally by microagglutination (confirmed by Western blot) and was consistent w ith the findings of multiple serogroups of VTEC found in the mettwurst incr iminated as the source, and suggests further strains (not found in the sour ce or in patients' faeces) were probably also involve ed. In HUS associated with; EHEC infection, multiple strain infection may be the rule rather tha n the exception. A relationship with clinical severity deserves further inv estigation. Non-O157 EHEC (in addition to O157) should be sought in all fut ure outbreaks of EHEC disease.