title: Variants of astA gene among extra-intestinal Escherichia coli of human and avian origin.
abstract: Many Escherichia coli strains harbour astA, which is the gene encoding the enteroaggregative E. coli heat-stable enterotoxin (EAST1). This gene is embedded in a putative transposase (ORF1) and presents polymorphism in diarrheagenic strains. Although astA and orf1 are detected in extraintestinal strains, little is known about polymorphism and differential gene transcription in this pathotype. In the present work, extraintestinal E. coli from humans (ExPEC - Extraintestinal Pathogenic E. coli) and poultry (APEC - Avian Pathogenic E. coli) were assayed to verify the presence of astA/orf1 and possible polymorphisms in these genes. Three astA/orf1 patterns were detected via Sanger sequencing. Pattern 1 was novel and represented an astA pseudogene. Pattern 2 and pattern 3 presented distinct amino acids within the reading frame encoding astA and were identical to the sequences found in EAEC 17-2 and EAEC 042, respectively. Regarding the frame encoding ORF1, all mutations detected in the three patterns were neutral. The transcripts of astA/orf1 in vitro were underregulated in strains possessing the pattern 1 sequence. The results demonstrate that the same astA sequences may be detected in diarrheagenic and extra-intestinal E. coli. However, extraintestinal isolates may also present an astA pseudogene that has not been reported in diarrheagenic E. coli.
authors.affiliation: Bacterial Molecular Biology Laboratory, Department of Genetics, Evolution and Bioagents, Institute of Biology, State University of Campinas (UNICAMP), CEP 13083-875, Campinas, SP, Brazil.
authors.forename: Renato Pariz
authors.initials: RP
authors.lastname: Maluta
authors.affiliation: Bacterial Molecular Biology Laboratory, Department of Genetics, Evolution and Bioagents, Institute of Biology, State University of Campinas (UNICAMP), CEP 13083-875, Campinas, SP, Brazil.
authors.forename: Janaína Luisa
authors.initials: JL
authors.lastname: Leite
authors.affiliation: Bacterial Molecular Biology Laboratory, Department of Genetics, Evolution and Bioagents, Institute of Biology, State University of Campinas (UNICAMP), CEP 13083-875, Campinas, SP, Brazil.
authors.forename: Thaís Cabrera Galvão
authors.initials: TCG
authors.lastname: Rojas
authors.affiliation: Department of Microbiology, Department of Immunobiology and Parasitology, Federal University of São Paulo (UNIFESP), CEP 04021-001, São Paulo, SP, Brazil.
authors.forename: Isabel Cristina Affonso
authors.initials: ICA
authors.lastname: Scaletsky
authors.affiliation: Instituto Biológico, CAPTAA, Unidade de Pesquisa e Desenvolvimento de Bastos, CEP 17690-000, Bastos, SP, Brazil.
authors.forename: Elisabete Aparecida Lopes
authors.initials: EAL
authors.lastname: Guastalli
authors.affiliation: Department of Internal Medicine, School of Medicine, State University of Campinas (UNICAMP), CEP 13083-894, Campinas, SP, Brazil.
authors.forename: Marcelo de Carvalho
authors.initials: MC
authors.lastname: Ramos
authors.affiliation: Bacterial Molecular Biology Laboratory, Department of Genetics, Evolution and Bioagents, Institute of Biology, State University of Campinas (UNICAMP), CEP 13083-875, Campinas, SP, Brazil.
authors.forename: Wanderley
authors.initials: W
authors.lastname: Dias da Silveira
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001427:Bacterial Toxins / Q000737:chemistry / Q000235:genetics*; D001483:Base Sequence; D004768:Enterotoxins / Q000737:chemistry / Q000235:genetics*; D004926:Escherichia coli / Q000145:classification / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics*; D005798:Genes, Bacterial; D014644:Genetic Variation; D006801:Humans; D008958:Models, Molecular; D011487:Protein Conformation; D017422:Sequence Analysis, DNA; D065288:Serogroup; D014774:Virulence / Q000235:genetics
chemical_list: D001427:Bacterial Toxins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; C034151:heat stable toxin (E coli)
keywords: APEC; EAST1; Escherichia coli; ExPEC; transposase