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

Abstract

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.

Molecular Characterization of Diarrheagenic Escherichia coli from Libya

“…Several workers reported relatively similar results. 15,45 Recently, Harrington and others 46 suggested the term "typical EAEC" to refer to strains expressing the aggR regulon. Results of this study show an abundance of typical rather than atypical EAEC among diarrheic Libyan children, as reported elsewhere.…”

“…For this reason, additional virulence genes have been used to screen EAEC-positive E. coli that include: aggR, a transcriptional activator; aggA, fimbriae AAFI; aafA, fimbriae AAF II; agg3A, fimbriae AAF III; astA, aggregative stable toxin 1 (EAST 1); pet, plasmid-encoded heat-labile toxin; aap, antiaggregation protein; and pic, protein involved in colonization. [12][13][14][15][16][17][18][19] High isolation rates of DEC, particularly EAEC, among diarrheic children have been reported from some developing countries. Vargas and others 20 determined the distribution of enteropathogens, including bacteria, viruses, and parasites, causing diarrhea among children 5 years of age in Ifakara, Tanzania.…”

“…Furthermore, PCR techniques were used to screen all EAEC-positive E. coli for virulence genes. [12][13][14][15][16][17][18][19] Primer sequences, the amplification program, and expected amplicon sizes are shown in Table 1. Whole-cell lysates, obtained by boiling 28 or QIAamp DNA Mini Kit (Qiagen, Valencia, CA), from each isolate were used as DNA template.…”

Enteroaggregative Escherichia coli in diarrheic children in Egypt: molecular characterization and antimicrobial susceptibility

“…These included: pCVD432 encoding for EAEC; eaeA and bfpA for EPEC; stx1and stx2 for Shiga-like toxin 1 (SLT-1) and Shiga-like toxin 2 (SLT-2), respectively, for STEC; estA1 and estA2-4 for heat-stable (ST) and eltB for heat-labile (LT) toxins of ETEC; and ipaH for EIEC. Also, PCR techniques [14][15][16][17][18][19][20][21] were used to screen all E. coli isolates for EAEC-associated virulence genes including: aggR, a transcriptional activator; aggA, fimbriae AAFI; aafA, fimbriae AAF II; agg3A, fimbriae AAF III; astA, aggregative stable toxin 1 (EAST 1); pet, plasmid-encoded heat-labile toxin; aap, anti-aggregation protein; and pic, protein involved in colonization. In addition, ETEC-positive E. coli isolates were examined for coli surface antigens (CS) by PCR [13].…”

An assessment of potential public health risk associated with the extended survival of indicator and pathogenic bacteria in freshwater lake sediments

“…However, certain pathogenic serotypes of E. coli such as enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC), enterohemorrhagic E. coli (EHEC), enteropathogenic E. coli (EPEC) enteroaggregative E. coli (EAggEC) and enteroadhesive E. coli (DAEC) have been reported as an emerg- ing public health concern for children in developing countries (Kaper et al, 2004) including India where frequent outbreaks have been reported (Kahali et al, 2004). Vibrio parahaemolyticus is a natural inhabitant of marine and estuarine environments which has been recognized as an important cause of food borne illness in Asia and United States and most of the outbreaks are associated with consumption of raw or undercooked shellfish (Daniels et al, 2000).…”