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KMID : 1134820160450040577
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Journal of the Korean Society of Food Science and Nutrition
2016 Volume.45 No. 4 p.577 ~ p.584
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Acid Resistance of Non-O157 Shiga Toxin-Producing Escherichia coli Adapted in Fruit Juices in Simulated Gastric Fluid
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Kim Gwang-Hee
Oh D. H.
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Abstract
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The objectives of this study were Ⅰ) to compare the acid resistance (AR) of seven non-O157 Shiga toxin-producing Escherichia coli (STEC) serogroups, including O26, O45, O103, O111, O121, O145, and O157:H7 STEC isolated from various sources, in 400 mM acetic acid solution (AAS) at pH 3.2 and 30°C for 25 min with or without glutamic acid and Ⅱ) to determine strain survival upon exposure to simulated gastric fluid (SGF, pH 1.5) at 37°C for 2 h after acid adaptation in apple, pineapple, orange, and strawberry juices at pH 3.8, 4°C and 20°C. Results show that the O111 serogroup strains had the strongest AR (0.12 log reduction CFU/mL) which was very similar to that of O157:H7 STEC (P>0.05), compared to other serogroups in AAS without glutamic acid, whereas O26 serogroup strains showed the most sensitive AR. However, there was no significant (P>0.05) difference of AR among seven serogroups in AAS with glutamic acid. In the SGF study, 05-6545 (O45:H2), 08023 (O121:H19), and 03-4669 (O145:NM) strains adapted in fruit juices at 4°C and 20°C displayed enhanced survival with exposure to SGF for 60 min compared to 06E0218 (O157:H7) strains (P<0.05). In addition, 4 STEC strains adapted in pineapple juice at 4°C showed enhanced survival with exposure to SGF for 60 min compared to those strains acid-adapted in the other fruit juices. Generally, adaptation at 4°C in fruit juices resulted in significantly enhanced survival levels compared to acid-adapted at 20°C and non-adapted conditions. The AR caused by adaptation in fruit juices at low temperature may thus increase survival of non-O157 STEC strain in acidic environments such as the gastrointestinal tract. These results suggest that more careful strategies should be provided to protect against risk of foodborne illness by non-O157 STEC.
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KEYWORD
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acid resistance, Shiga toxin-producing Escherichia coli non-O157, simulated gastric fluid, glutamic acid, fruit juices
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