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Editor,—We read with interest the article by Blanshard et al (Gut 1996; 39:824–32) where a cohort of adult AIDS patients with chronic diarrhoea was investigated for potential stool pathogens. An extensive array of diagnostic tools was used, including microbiological examination of stools, duodenal aspirates, and microscopic examination of biopsy specimens from the duodenum, jejunum, and rectum. However, despite investigation for at least 20 bacterial, viral, and parasitic pathogens it seems a remarkable omission that no pathogenic Escherichia coli groups were sought.
Although routine microbiology laboratories now rarely seek stoolE coli, other than enterohaemorrhagic E coliof serogroup O157, these organisms are readily isolated on MacConkey agar, and categories may be further differentiated using DNA probes or in vitro cell culture assays, or both, in the absence of serotyping facilities.1 Although one pilot study has found no evidence of a role for enteroadherent E coli in diarrhoea in HIV infected patients,2 several others report such an association. Case reports have suggested that enteropathogenic E coli (EPEC)3 ,4 and enteroaggregative E coli (EAEC)5 are possible causes of chronic diarrhoea in adult patients with AIDS and several groups have shown a highly significant association between HEp-2 cell-adherent E coli (including EPEC and EAEC) and chronic diarrhoea in adults with AIDS in Zambia6 and the USA.7 ,8 In the latter two studies, as with Blanshard et al’s study, light and electron microscopic techniques were used to examine intestinal biopsy samples. In the preliminary study 17% of patients with AIDS had bacteria adherent to their intestinal mucosa in patterns indicative of several pathogenic E coligroups.7 The other study reported 52 patients with chronic diarrhoea and mucosally adherent bacteria associated with attaching/effacing lesions (characteristic of EPEC) or loosely associated with the mucosa (EAEC).8
Although Blanshard et al were able to identify a potential pathogen in 83% of cases, the available literature suggests that pathogenic E coli could have accounted for a considerable percentage of those cases where no pathogen was found.
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