Enteroaggregative Escherichia coli (EAEC) is recognized as an emerging cause of diarrhea in children and adults worldwide, and recent studies have implicated EAEC in persistent diarrhea in patients infected with human immunodeficiency virus (HIV). In this study, we identified aggregative adhesion fimbria type III (AAF-III) in isolate 55989, a typical EAEC strain. Analysis of the sequence of the plasmid-borne agg-3 gene cluster encoding AAF-III showed this cluster to be closely related to the agg and aaf operons and to the afa operons carried by diffusely adherent pathogenic E. coli. We investigated the adhesion properties of a collection of 25 EAEC strains isolated from HIV-infected patients presenting with persistent diarrhea. We found that a minority of strains (36%) carried sequences similar to those of the agg and aaf operons, which encode AAF-I and AAF-II, respectively. We developed PCR assays specific for the agg-3 operon. In our collection, the frequency of AAF-III strains was similar (12%) to that of AAF-I strains (16%) but higher than that of AAF-II isolates (0%). Differences between EAEC strains in terms of the virulence factors present render detection of these strains difficult with the available DNA probes. Based on comparison of the agg, aaf, and agg-3 operons, we defined an AAF probe internal to the adhesion gene clusters and demonstrated that it was efficient for the identification of EAEC strains. We investigated 32 EAEC isolates, of which only 34.4% were detected with the classical CVD432 probe (detecting pAA virulence plasmids) whereas 65.6% were detected with the AAF probe.

In human immunodeficiency virus (HIV)-infected adults from the Central AfricanRepublic, the occurrence of chronic diarrhea due to HEp-2 adherent Escherichia coli (EAEC) harboring virulence markers (eaeA, BFP, EAF, astA determinant of EAST/1, positive FAS test, enteropathogenic E. coli O serogroup) was shown to be associated with AIDS. We also show that EAEC that produce verotoxin (Stx2) but do not harbor the genetic markers for classical enterohemorrhagic E. coli are involved in hemorrhagic colitis and hemolytic-uremic syndrome in patients with HIV.The Central African Republic is strongly affected by the human immunodeficiency virus (HIV) epidemic (24). Nearly 72% of the adults hospitalized with AIDS present initially with chronic diarrhea (CD) (14). Between 1996 and 1999 we used phenotypic (14) and genotypic assays to study 88 HIV-infected adults hospitalized in Bangui and their matched controls to determine the clinical significance of diarrheagenic Escherichia coli (7,8,9,10,12,16,22,25,27,29,31,32,34,35). The methods were as previously described (14). To be included in the study, the patients had to be HIV positive and aged 18 or over, have CD (3 or more loose watery stools per day for at least 14 days [3]), have E. coli in a stool sample, and give informed consent. Each patient was matched with a control recruited from among the neighbors and family members of the patient. The matching criteria dictated that the control be aged within 5 years of the patient's age and of the same sex. The recruitment criteria for the matched controls were as follows: testing positive for HIV antibodies, having had no diarrhea on the day of recruitment or during the previous month, and having E. coli in their stools on the day of recruitment. All controls gave informed consent to participate.HEp-2 adherent E. coli (EAEC) (5, 28) with localized adherent (LA), aggregative adherent (AA), or diffuse adherent (DA) patterns were more common in the patients (P Ͻ 10 Ϫ5 ) than in the controls (Table 1). Some EAEC exhibited a strong LA pattern (16 patients versus no control) in which Ͼ20% of the randomly selected cells had attached bacteria (11,19).These LA strains with a strong LA pattern were associated with CD, especially when the assays used to identify enteropathogenic E. coli (EPEC) virulence factors yielded positive results (eaeA, EPEC adherence factor [EAF] plasmid, bundleforming pili [BFP] PCR, and fluorescent actin staining [FAS] test) (P Ͻ 10 Ϫ5 ), and all belonged to known EPEC O serogroups (P ϭ 0.0001). The isolation of enteroaggregative E. coli (EAggEC) was strongly correlated with the presentation of CD (P Ͻ 10 Ϫ5 ). The difference in the isolation rates of EAEC strains exhibiting DA between patients and controls was only significant when the presence of the astA gene encoding EAST/1 was considered (P ϭ 0.016); astA was located on 7-to 40-kb plasmids.Interestingly, all of the enteric bacteria isolated from 42 patients (86% of the 49 patients with severe immunodepression) harboring EAEC with virulence factors were E. co...