title: Identification of new heat-stable (STa) enterotoxin allele variants produced by human enterotoxigenic Escherichia coli (ETEC).
abstract: We describe natural variants of the heat stable toxin (STa) produced by enterotoxigenic Escherichia coli (ETEC) isolates collected worldwide. Previous studies of ETEC isolated from human diarrheal cases have reported the existence of three natural STa gene variants estA1, estA2 and estA3/4 where the first variant encodes STp (porcine, bovine, and human origin) and the two latter ones encode STh (human origin). We identified STa sequences by BLASTn and profiled ST amino acid polymorphisms in a collection of 118 clinical ETEC isolates from children and adults from Asia, Africa and, Latin America that were characterized by whole genome sequencing. Three novel variants of STp and STh were found and designated STa5 and STa6, and STa7, respectively. Presence of glucose significantly decreased the production of STh and STp toxin variants (p<0.05) as well as downregulated the gene expression (STh: p<0.001, STp: p<0.05). We found that the ETEC isolates producing the most common STp variant, STa5, co-expressed coli surface antigen CS6 and was significantly associated with disease in adults in this data set (p<0.001). Expression of mature STa5 peptide as well as gene expression of tolC, involved in ST secretion, increased in response to bile (p<0.05). ETEC expressing the common STh variant STa3/4 was associated with disease in children (p<0.05). The crp gene, that positively regulate estA3/4 encoding STa3/4, and estA3/4 itself had decreased transcriptional levels in presence of bile. Since bile levels in the intestine are lower in children than adults, these results may suggest differences in pathogenicity of ETEC in children and adult populations.
authors.affiliation: Department of Microbiology and Immunology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden; Institute of Molecular Biology and Biotechnology, Universidad Mayor de San Andrés, La Paz, Bolivia. Electronic address: enrique.joffre@ki.se.
authors.forename: Enrique
authors.initials: E
authors.lastname: Joffré
authors.affiliation: Department of Microbiology and Immunology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden; The Wellcome Trust Sanger Institute, Hinxton, Cambridge, United Kingdom.
authors.forename: Astrid
authors.initials: A
authors.lastname: von Mentzer
authors.affiliation: Department of Microbiology and Immunology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Ann-Mari
authors.initials: AM
authors.lastname: Svennerholm
authors.affiliation: Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Åsa
authors.initials: Å
authors.lastname: Sjöling
mesh_terms: D000328:Adult; D000349:Africa; D000483:Alleles; D001208:Asia; D001427:Bacterial Toxins / Q000235:genetics*; D002648:Child; D054307:Enterotoxigenic Escherichia coli / Q000235:genetics* / Q000302:isolation & purification* / Q000378:metabolism; D004768:Enterotoxins / Q000235:genetics* / Q000378:metabolism; D004927:Escherichia coli Infections / Q000382:microbiology*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D005947:Glucose / Q000378:metabolism; D006801:Humans; D007843:Latin America
chemical_list: D001427:Bacterial Toxins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; C034151:heat stable toxin (E coli); D005947:Glucose
keywords: Allele variants; Bile; Diarrhea; ETEC; Glucose; Heat stable toxin