title: Acid resistance and verocytotoxin productivity of enterohemorrhagic Escherichia coli O157:H7 exposed to microwave.
abstract: We examined the acid resistance and verocytotoxin (VT) productivity of enterohemorrhagic Escherichia coli O157:H7 irradiated by microwave with a domestic microwave oven and a commercial microwave radiator equipped with a thermo-regulator. When the cell suspension (5 mL) chilled at 0 °C was treated with a domestic microwave oven at weak power (2.45 GHz, 100 W) for 60 s, the living cell number was reduced by 2 orders (final temperature, about 65 °C). The surviving cells showed lower acid resistance and VT productivity than nonirradiated cells. To examine the nonthermal effect of microwave on acid resistance and VT productivity, the cells in Luria-Bertani medium were intermittently irradiated to keep the culture temperature at 37 °C with the microwave radiator (2.45 GHz, 0.6 W/mL). The intermittent radiation slightly reduced the acid resistance, but clearly suppressed the VT productivity. Microwave oven is probably useful for reducing not only the living cell number but also the acid resistance and VT productivity of EHEC O157:H7.
authors.affiliation: Dept. of Life Science, Graduate School of Integrated Arts and Sciences, Univ. of Tokushima, 1-1 Minamijosanjima-cho, Tokushima 770-8502, Japan.
authors.forename: Makiko
authors.initials: M
authors.lastname: Tsuji
authors.forename: Kumio
authors.initials: K
authors.lastname: Yokoigawa
mesh_terms: D015169:Colony Count, Microbial; D004927:Escherichia coli Infections / Q000382:microbiology / Q000517:prevention & control; D019453:Escherichia coli O157 / Q000302:isolation & purification / Q000378:metabolism* / Q000472:pathogenicity / Q000528:radiation effects*; D005243:Feces / Q000382:microbiology; D005514:Food Irradiation; D005517:Foodborne Diseases / Q000382:microbiology / Q000517:prevention & control; D006358:Hot Temperature; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007564:Japan; D050296:Microbial Viability / Q000528:radiation effects*; D008872:Microwaves; D022622:Shiga Toxin 1 / Q000378:metabolism*; D022641:Shiga Toxin 2 / Q000378:metabolism*; D022603:Shiga Toxins / Q000378:metabolism; D013045:Species Specificity; D013997:Time Factors; D014774:Virulence / Q000528:radiation effects
chemical_list: D022622:Shiga Toxin 1; D022641:Shiga Toxin 2; D022603:Shiga Toxins; C430449:verocytotoxin 2