Virulence Markers of Enteroaggregative Escherichia coli Isolated from Children and Adults with Diarrhea in Brasília, Brazil

Abstract

Escherichia coli strains isolated from sporadic cases of acute diarrhea in children and adults and from children without diarrhea were investigated for the presence of the pAA plasmid. Strains harboring the pAA plasmid were isolated at similar frequencies from children with (19.6%) and without (10.8%) diarrhea and from adults with diarrhea (11.8%). The genotypic and phenotypic virulence markers of these strains were further analyzed. Most of the strains were positive for EAST1 (73%), and this toxin was detected significantly more frequently in strains from children with diarrhea than in strains from adults with diarrhea (P < 0.05). Likewise, pic sequences were detected significantly more frequently in strains from children with diarrhea than in strains from adults with diarrhea (P < 0.005) and controls (P < 0.025). Furthermore, the association of pAA positivity (pAA ؉ ) and pic positivity (pic ؉ ) was more frequently found for strains from children with diarrhea than for strains from controls, indicating that pAA ؉ pic ؉ strains may represent a subset of pAA ؉ strains associated with disease in children. Most of the strains (82.5%) adhered to cells presenting the typical aggregative pattern. The frequency of occurrence of enteropathogenic E. coli (EPEC) serogroups in the strains from children with diarrhea was very high (56%), while none of the strains from adults with diarrhea belonged to EPEC serogroups. Extraintestinal virulence markers were very commonly found in strains from adults with diarrhea. The frequencies of occurrence of the adhesins AFA and SFA were significantly higher in strains from adults with diarrhea than in strains from children with diarrhea. More than one extraintestinal virulence marker was found in 58% of the strains from adults with diarrhea but in only 7.7% of the strains from children with diarrhea. Our results show that pAA ؉ strains isolated from children and adults with diarrhea present very different profiles when enteroaggregative E. coli virulence markers, serotypes, and extraintestinal virulence markers are considered.Several studies have reported on the association of enteroaggregative Escherichia coli (EAEC) with diarrheal disease in children (3,4,13,17,21,23,33). The EAEC pathotype has been defined by its aggregative pattern of adherence to tissue culture cells, but this definition seems to cover heterogeneous groups of strains, as indicated in volunteer studies (26) and investigations of the natural occurrence of the disease (3, 13, 14, 17). Nataro et al. (26) carried out a volunteer study with four different EAEC strains and showed that three of them failed to elicit diarrhea. Several epidemiological studies reported on an association of EAEC strains with sporadic diarrhea, either acute or persistent, and outbreaks in different geographic locations (3,13,17,21,23,33). Furthermore, Steiner et al. (44) reported on an association of EAEC with growth impairment even in the absence of diarrheal symptoms. However, in some case-control investigations, EAEC strains were isolated...

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

“…Even though EAEC infections persist in the presence of infections with other pathogens, none of the patients had infections caused by other pathotypes of diarrheagenic E. coli. As reported by many investigators (22,38,40,53), the majority of the EAEC isolates in our study remained Oantigen untypeable (62%). Similar to a recent report from Brazil (59), the prevalence of serogroup O44 was comparatively high in this study.…”

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

“…Except for a study conducted in Nigeria (19), in which the presence of genes related to AAF/II was associated with diarrhea in children, none of the pAA markers has been statistically associated with diarrhea, until now. Recently, Piva et al (20) detected pic sequences significantly more frequently in EAEC probe-positive strains from children with diarrhea than from controls.…”

“…Recently, Piva et al (20) detected EAST-1 in 73% of EAEC probe-positive strains. The astA gene has been detected not only in EAEC strains but also in EPEC, enterotoxigenic E. coli, Shiga-toxin producing E. coli, and enteroinvasive E. coli strains (6,28,32).…”

Characteristics of the enteroaggregative Shiga toxin/verotoxin-producing Escherichia coli O104:H4 strain causing the outbreak of haemolytic uraemic syndrome in Germany, May to June 2011

“…EAggEC is best known for its role in persistent diarrhoea (>14 days) in infants and children in developing countries. Studies in Mongolia [27], India [28], Brazil [29,30], Nigeria [31,32], Israel [33], Venezuela [34], Congo [35] and many other countries, have identified EAggEC as a highly prevalent (often the most prevalent) E. coli pathotype in infants. Further, the role of EAggEC as an important pathogen in AIDS patients continues to develop, and EAggEC now ranks among the most important enteric pathogens in this population group [36,37].…”