title: Acid Resistance and Molecular Characterization of Escherichia coli O157:H7 and Different Non-O157 Shiga Toxin-Producing E. coli Serogroups.
abstract: The objective of this study was to compare the acid resistance (AR) of non-O157 Shiga toxin-producing Escherichia coli (STEC) strains belonging to serogroups O26, O45, O103, O104, O111, O121, and O145 with O157:H7 STEC isolated from various sources in 400 mM acetic acid solutions (AAS) at pH 3.2 and 30 °C for 25 min with or without glutamic acid. Furthermore, the molecular subgrouping of the STEC strains was analyzed with the repetitive sequence-based PCR (rep-PCR) method using a DiversiLab(TM) system. Results for a total of 52 strains ranged from 0.31 to 5.45 log reduction CFU/mL in the absence of glutamic acid and 0.02 to 0.33 CFU/mL in the presence of glutamic acid except for B447 (O26:H11), B452 (O45:H2), and B466 (O104:H4) strains. Strains belonging to serogroups O111, O121, and O103 showed higher AR than serotype O157:H7 strains in the absence of glutamic acid. All STEC O157:H7 strains exhibited a comparable DNA pattern with more than 95% similarity in the rep-PCR results, as did the strains belonging to serogroups O111 and O121. Surprisingly, the DNA pattern of B458 (O103:H2) was similar to that of O157:H7 strains with 82% similarity, and strain B458 strain showed the highest AR to AAS among the O103 strains with 0.44 log reduction CFU/mL without glutamic acid. In conclusion, STEC serotypes isolated from different sources exhibited diverse AR and genetic subtyping patterns. Results indicated that some non-O157 STEC strains may have higher AR than STEC O157:H7 strains under specific acidic conditions, and the addition of glutamic acid provided enhanced protection against exposure to AAS.
authors.affiliation: Dept. of Food Science and Biotechnology, Kangwon Natl. Univ, 1 Kangwondaehak-gil, Chuncheon-si, Gangwon-do, 200-701, South Korea.
authors.forename: Gwang-Hee
authors.initials: GH
authors.lastname: Kim
authors.affiliation: USDA, Agricultural Research Service, Food Science Research Unit, Dept. of Food, Bioprocessing and Nutrition Sciences, North Carolina State Univ, Raleigh, N.C., 27695, U.S.A.
authors.forename: Frederick
authors.initials: F
authors.lastname: Breidt
authors.affiliation: USDA, Agricultural Research Service, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, Pa., 19038, U.S.A.
authors.forename: Pina
authors.initials: P
authors.lastname: Fratamico
authors.affiliation: Dept. of Food Science and Biotechnology, Kangwon Natl. Univ, 1 Kangwondaehak-gil, Chuncheon-si, Gangwon-do, 200-701, South Korea.
authors.forename: Deog-Hwan
authors.initials: DH
authors.lastname: Oh
mesh_terms: D019342:Acetic Acid / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000032:analysis*; D019453:Escherichia coli O157 / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins; D016133:Polymerase Chain Reaction; D065288:Serogroup; D022603:Shiga Toxins; D054323:Shiga-Toxigenic Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism
chemical_list: D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D022603:Shiga Toxins; D019342:Acetic Acid
keywords: DiversiLabTM system; E. coli non-O157; acid resistance; glutamic acid; repetitive sequence-based PCR