title: Identification and epidemiological description of enterohemorrhagic Escherichia coli O157 strains producing low amounts of Shiga toxin 2 in Aichi Prefecture, Japan.
abstract: Out of 68 Escherichia coli O157 field isolates tested in vitro for Shiga toxin (Stx) 2 production, 12 (17.6%) produced no or a limited amount of Stx2 (Stx 2 non- or low-producing strain; TNLP) even though all 68 possessed the stx(2) gene. The remaining 56 were Stx2 high-producing strains. The 12 TNLPs carried the q21 gene allele, which encodes a transcription antiterminator Q protein and is highly homologous to that of phi21 phage. They also carried nucleotide substitutions and insertions in the promoter region of the stx(2) gene compared with that of O157 EDL933, producing a considerable amount of Stx2. In contrast, the Stx2 high-producing strains carried the q933 gene allele, which was first reported on an stx(2) phage (933W), but not the q21 gene allele, and did not have mutations in the promoter region of the stx(2) gene. These 2 genetic characteristics, i.e., replacement of the q gene and mutation in the promoter region of the stx(2) gene, seemed to determine the amount of Stx2 produced by each strain. The TNLPs were more frequently isolated from healthy carriers than from patients (P<0.05), suggesting that TNLPs are less virulent than those with normal Stx2 production.
authors.affiliation: Department of Microbiology, Aichi Prefectural Institute of Public Health, Nagoya, Japan. masakado_matsumoto@pref.aichi.lg.jp
authors.forename: Masakado
authors.initials: M
authors.lastname: Matsumoto
authors.forename: Masahiro
authors.initials: M
authors.lastname: Suzuki
authors.forename: Masao
authors.initials: M
authors.lastname: Takahashi
authors.forename: Kaoru
authors.initials: K
authors.lastname: Hirose
authors.forename: Hiroko
authors.initials: H
authors.lastname: Minagawa
authors.forename: Michio
authors.initials: M
authors.lastname: Ohta
mesh_terms: D002353:Carrier State / Q000453:epidemiology* / Q000382:microbiology; D016521:Electrophoresis, Gel, Pulsed-Field; D004927:Escherichia coli Infections / Q000453:epidemiology* / Q000382:microbiology; D019453:Escherichia coli O157 / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity; D006801:Humans; D007564:Japan / Q000453:epidemiology; D009154:Mutation; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D011401:Promoter Regions, Genetic; D022641:Shiga Toxin 2 / Q000096:biosynthesis* / Q000235:genetics*; D014764:Viral Proteins / Q000235:genetics; D014774:Virulence
chemical_list: C066119:Q protein, Bacteriophage lambda; D022641:Shiga Toxin 2; D014764:Viral Proteins