Short report: characterization of enteroaggregative Escherichia coli isolates from Iranian children.

Bouzari, Saeid; Jafari, Ameneh; Azizi, Armaghan; Oloomi, Mana; Nataro, James P.

doi:10.4269/ajtmh.2001.65.13

Cited by 25 publications

(17 citation statements)

References 17 publications

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“…In that study, they suggested that the EAEC probe-positive strains might have a higher pathogenic potential or, alternatively, that EAEC probenegative strains may harbor virulence factors that have not yet been described. In contrast, Bouzari et al (3) found that EAEC probe-negative strains in Iran share virulence factors with EAEC probe-positive isolates. Our findings, along with those of Elias et al (7), suggest the possibility that EAEC probe-positive strains comprise a distinct subcategory of EAEC that could be called typical EAEC.…”

Section: Discussionmentioning

confidence: 96%

Enteroaggregative Escherichia coli Virulence Factors Are Found To Be Associated with Infantile Diarrhea in Brazil

Zamboni¹,

Fabbricotti²,

Fagundes-Neto

et al. 2004

J Clin Microbiol

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We have previously shown that enteroaggregative Escherichia coli (EAEC) is an important pathogen among Brazilian infants. Most EAEC strains harbor a plasmid (pAA) from which a DNA fragment has been used as a probe (EAEC probe). To better understand the characteristics of EAEC in Brazil, 109 strains carrying and lacking the EAEC probe sequence were tested for the presence of pAA plasmid-borne and chromosomal factors. Common virulence factors of probe-positive and probe-negative isolates included the presence of the Pet, EAST-1, Shf, Irp2, ShET1/Pic, and Hly virulence markers. The presence of AggR or one other virulence factor (AAF/I, AAF/II, AAF/III, or Aap) was predominantly identified only in probe-positive strains. In EAEC probepositive strains, the virulence marker Aap was found significantly more frequently (P ‫؍‬ 0.023) in isolates from children with diarrhea (22%) than in isolates from controls (3%). EAST-1 and Shf were the markers most frequently detected (61%) in EAEC probe-negative strains and were found to be significantly associated with diarrhea (P ‫؍‬ 0.003 and P ‫؍‬ 0.020, respectively). Furthermore, our data suggest that AggR can be used as an important genetic marker for EAEC probe-positive strains.Enteroaggregative Escherichia coli (EAEC) is increasingly recognized as a cause of diarrhea worldwide (18). EAEC is defined by its characteristic "stacked brick" aggregative adherence (AA) pattern of adherence to HEp-2 cell (17). Most EAEC strains harbor a 60-to 65-MDa virulence plasmid (pAA). A 1-kb fragment of pAA, referred to as the EAEC probe or CVD432 (1), has been widely used for epidemiological studies (7,19,25,29). The pAA plasmid also encodes AA fimbriae (AAF) I, II, and III (2, 4, 15); the transcriptional activator AggR (16); enteroaggregative heat-stable enterotoxin 1 (EAST-1) (23); a 104-kDa cytotoxin designated Pet (8); the cryptic secreted protein Shf (5); and a novel antiaggregation protein (dispersin) encoded by the aap gene (formerly known as aspU) (27). In addition to the pAA plasmid, some EAEC strains express putative virulence factors that are encoded on the chromosome, including a 116-kDa secreted mucinase (Pic) (12), yersiniabactin (26), and the E. coli ␣-hemolysin (30). Shigella enterotoxin 1 (ShET1) is encoded by the antisense strand of the pic gene (10, 21). However, none of these factors is consistently found in all EAEC isolates, as determined by hybridization studies.To find a specific virulence marker for the detection of EAEC in epidemiological and clinical studies, we tested 109 strains, isolated from Brazilian children in a previously described study (25), for their abilities to hybridize to eight pAA plasmid-derived and three chromosomal gene probes. MATERIALS AND METHODSBacterial strains. The strains examined in this work were isolated during a study of the epidemiology of acute diarrhea in children less than 2 years old conducted in different regions of Brazil from 1997 to 1999 (25). The children were admitted to public hospitals in the following cities (states) for t...

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Section: Discussionmentioning

confidence: 96%

Enteroaggregative Escherichia coli Virulence Factors Are Found To Be Associated with Infantile Diarrhea in Brazil

Zamboni¹,

Fabbricotti²,

Fagundes-Neto

et al. 2004

J Clin Microbiol

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“…EAEC was discovered in 15.1% of cases in the diarrheal group and appeared to be the most prevalent pathogen among DEC categories. These cases seem to be the first EAEC infec- (3,4,12,24,36). The pathogenic mechanisms of EAEC infection are only partially understood and are most consistent with mucosal colonization followed by secretion of enterotoxins and cytotoxins.…”

Section: Discussionmentioning

confidence: 99%

Typical Enteroaggregative Escherichia coli Is the Most Prevalent Pathotype among E. coli Strains Causing Diarrhea in Mongolian Children

et al. 2004

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Diarrhea remains one of the main sources of morbidity and mortality in the world, and a large proportion is caused by diarrheagenic Escherichia coli. In Mongolia, the epidemiology of diarrheagenic E. coli has not been well studied. A total of 238 E. coli strains from children with sporadic diarrhea and 278 E. coli strains from healthy children were examined by PCR for 10 virulence genes: enteropathogenic E. coli (EPEC) eae, tir, and bfpA; enterotoxigenic E. coli (ETEC) lt and st; enteroinvasive E. coli (EIEC) ipaH; enterohemorragic E. coli stx1 and stx2; and enteroaggregative E. coli (EAEC) aggR and astA. EAEC strains without AggR were identified by the HEp-2 cell adherence test. The detection of EAEC, ETEC, EPEC, and EIEC was significantly associated with diarrhea. The incidence of EAEC (15.1%), defined by either a molecular or a phenotypic assay, was higher in the diarrheal group than any other category (0 to 6.0%). The incidence of AggR-positive EAEC in the diarrheal group was significantly higher than in the control group (8.0 versus 1.4%; P ‫؍‬ 0.0004), while that of AggR-negative EAEC was not (7.1 versus 4.3%). Nineteen AggR-positive EAEC strains harbored other EAEC virulence genes-aggA, 2 (5.5%); aafA, 4 (11.1%); agg-3a, 5 (13.8%); aap, 8 (22.2%); aatA, 11 (30.5%); capU, 9 (25.0%); pet, 6 (16.6%); and set, 3 (8.3%)-and showed 15 genotypes. EAEC may be an important pathogen of sporadic diarrhea in Mongolian children. Genetic analysis showed the heterogeneity of EAEC but illustrated the importance of the AggR regulon (denoting typical EAEC) as a marker for virulent EAEC strains.Diarrhea continues to be one of the most common causes of morbidity and mortality among infants and children in developing countries (5, 18). Five distinct classes of diarrheagenic Escherichia coli (DEC) are recognized as being associated with diarrheal disease. They are enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC), enteropathogenic E. coli (EPEC), enterohemorrhagic E. coli (EHEC), and enteroaggregative E. coli (EAEC); diffuse adhering E. coli (DAEC) may represent a sixth category, but this has not been clearly established (18). Each class of DEC is defined on the basis of distinct virulence characteristics, and tests for these characteristics have been developed to distinguish DEC classes from each other and from nonpathogenic E. coli strains of the normal flora (15, 34). The epidemiological significance of each E. coli category in childhood diarrhea varies with the geographical area. It has become clear that there are important regional differences in the prevalences of the different categories of DEC. The incidences of diarrheal illnesses caused by the different categories of DEC were examined mainly in Latin America, Africa, southern and Southeast Asia, and the Middle East (1,3,25,32,35,36,45). Study of the prevalences of DEC categories and their importance in childhood diarrhea has not been carried out in Mongolia. Therefore, to define the association of various categories of E. coli with diarrhea in Mongolia, w...

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“…Molecular epidemiology may therefore be a useful tool for evaluating the pathogenicity of EAEC strains and has been used to identify the aafA gene, which encodes the structural subunit of AAF/II fimbriae, as a putative marker for potentially pathogenic strains (8,33). In this study, we employed strain collections obtained during case-control studies.…”

Section: Vol 42 2004 Iron Utilization In Eaec Strains 41mentioning

confidence: 99%

Molecular Epidemiology of the Iron Utilization Genes of Enteroaggregative Escherichia coli

et al. 2004

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Enteroaggregative Escherichia coli (EAEC) strains are etiologic agents of acute and persistent diarrhea. In this study, the results of phenotypic assays suggested that EAEC strains possess specialized iron acquisition systems. Genes required for the synthesis (iucA) or transport (fepC) of siderophores, and genes encoding siderophore (fyuA, ireA, and iroN) or heme transport (chu) receptors or hemoglobin proteases (pic and hbp), were sought in EAEC strains which have been characterized with respect to known virulence genes and phylogeny. The chuA, iucA, fyuA, fepC, and pic genes were detected in 33, 76.2, 85.7, 33, and 61.9% of these EAEC strains, respectively, and the other genes were absent. The majority of EAEC strains possessed genes encoding multiple iron transport systems, and there was no phylogenetic correlation in the distribution of the majority of these loci, as is typical for EAEC. The notable exceptions were chuA and fepC (which is associated with the prrA-modA-fepC pathogenicity island); these genes were restricted to the EAEC2 and DAEC2 phylogenetic groups, which could represent pathogenic subsets. When collections of EAEC strains isolated during casecontrol studies in Nigeria and Brazil were examined, no association of the presence of either chuA or iucA alone with diarrhea was seen, but both genes together were present in significantly more strains from cases than from controls in the Nigerian collection (P < 0.05). It is possible that the presence of both genes marks at least some virulent strains. The data also demonstrate geographical variation in the association of iron utilization genes with disease in EAEC.The pattern of mannose-resistant adherence to intestinal epithelial cells has been used to broadly classify Escherichia coli diarrheal isolates (31). The majority of nonpathogenic E. coli strains are nonadherent, while E. coli strains that adhere in a localized manner are almost invariably found to be enteropathogenic E. coli (EPEC). Diffuse adherence is seen in diffusely adherent E. coli (DAEC) and to varying degrees in other categories. Intestinal isolates of E. coli that adhere to epithelial cells in a characteristic stacked-brick pattern are categorized as enteroaggregative E. coli (EAEC) (31, 55). EAEC and DAEC strains are often recovered from healthy individuals, and the factors that dictate their adherence patterns differ among strains in each category. It is likely that at least some EAEC and DAEC strains are pathogenic while others are not. EAEC and DAEC remain enigmatic in some sense because their epidemiology and molecular pathogenesis are less well understood than those of other diarrhea-causing categories-EPEC and enterohemorrhagic, enterotoxigenic, and enteroinvasive E. coli (EHEC, ETEC, and EIEC, respectively). EAEC strains were originally recognized as predominant etiologic agents of persistent diarrhea in developing countries (5). In recent epidemiological studies, EAEC has been increasingly associated with acute as well as protracted diarrhea in several parts of the world...

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Short report: characterization of enteroaggregative Escherichia coli isolates from Iranian children.

Cited by 25 publications

References 17 publications

Enteroaggregative Escherichia coli Virulence Factors Are Found To Be Associated with Infantile Diarrhea in Brazil

Enteroaggregative Escherichia coli Virulence Factors Are Found To Be Associated with Infantile Diarrhea in Brazil

Typical Enteroaggregative Escherichia coli Is the Most Prevalent Pathotype among E. coli Strains Causing Diarrhea in Mongolian Children

Molecular Epidemiology of the Iron Utilization Genes of Enteroaggregative Escherichia coli

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