Characterization of enteroaggregative Escherichia coli isolates

Rich, C

doi:10.1016/s0378-1097(99)00056-7

Cited by 20 publications

(34 citation statements)

References 15 publications

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“…This finding is in agreement with those of a previous study with a worldwide collection of EAEC isolates (10) and a recent study conducted in Brazil (59). The prevalence of the AAF/II operon is generally reported to be low (13,41,52), and the results of our study are consistent with that finding. Bernier et al (4) have recently reported on the existence of a high level of heterogeneity in the AAF/II operon and demonstrated the use of an aafDA-specific probe for the detection of AAF/II.…”

Section: Discussionsupporting

confidence: 94%

“…The higher frequency of the accessory genes (aggC, aafC, and agg3C) in comparison to the lower frequency of the corresponding structural genes encoding pilin subunit provide evidence for the heterogeneity in the latter. These results are in agreement with those of the earlier studies on the higher prevalence of aggC genes (10,16,41). The presence of agg3C in 22.3% of the EAEC isolates indicated that the agg3 gene or a variant agg3 gene was the second most frequent adhesin after agg.…”

Section: Discussionsupporting

confidence: 93%

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Virulence Characteristics and Molecular Epidemiology of Enteroaggregative Escherichia coli Isolates from Hospitalized Diarrheal Patients in Kolkata, India

et al. 2004

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Enteroaggregative Escherichia coli (EAEC) is an important diarrheal enteropathogen defined by aggregative adherence to cultured epithelial cells. We have detected EAEC from 121 (6.6%) of 1,826 hospitalized patients admitted with diarrhea to the Infectious Diseases Hospital in Kolkata, India. Watery diarrhea was recorded significantly (P ‫؍‬ 0.0142) more often in children. The majority of the EAEC isolates were not serotypeable (62%) and showed resistance to five or more antibiotics (76%). We studied different virulence genes and the molecular epidemiology of 121 EAEC isolates recovered from diarrheal patients. A PCR assay for detection of virulence genes, an assay for determination of clump formation in liquid culture, and a HeLa cell adherence assay were carried out to characterize the EAEC isolates. Investigations were also conducted to correlate the virulence gene profiles with diarrheal symptoms and molecular epidemiology by pulsed-field gel electrophoresis (PFGE). Two or more virulence genes were detected in 109 (90.1%) EAEC isolates. In the cluster analysis, some isolates with specific gene profiles and phenotypes formed a group or subcluster. This study highlights the comparative distributions of three fimbrial adhesins and other virulence genes among EAEC isolates. The diverse virulence gene and PFGE profiles, along with the existence of diverse serotypes and antibiograms, suggests that the EAEC isolates are genetically heterogeneous in Kolkata.

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Section: Discussionsupporting

confidence: 94%

Section: Discussionsupporting

confidence: 93%

Virulence Characteristics and Molecular Epidemiology of Enteroaggregative Escherichia coli Isolates from Hospitalized Diarrheal Patients in Kolkata, India

et al. 2004

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“…A similar astA gene frequency has previously been reported among EAEC probe-negative strains (7), but in that study, EAST-1 was detected more frequently in strains from controls than in strains from patients. Okeke et al (19) and Rich et al (22) detected EAST-1 in 23 and 45% of EAEC strains, respectively, but no correlation between the presence …”

Section: Discussionmentioning

confidence: 95%

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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“…59 The prevalence of EAST-1 among EAEC strains and its contribution to virulence remains unclear. 60,61 Further toxins Figure 1. Enterotoxigenic E. coli (ETEC).…”

Section: Molecular Mechanisms Of Virulencementioning

confidence: 99%