Int. J. Environ. Res. Public Health 2013, 10(7), 2857-2870; doi:10.3390/ijerph10072857
Article

Evaluation of Models Describing the Growth of Nalidixic Acid-Resistant E. coli O157:H7 in Blanched Spinach and Iceberg Lettuce as a Function of Temperature

Received: 27 May 2013; in revised form: 1 July 2013 / Accepted: 3 July 2013 / Published: 9 July 2013
(This article belongs to the Special Issue Antimicrobial Resistance Prevention and Control)
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract: The aim of this study was to model the growth of nalidixic acid-resistant E. coli O157:H7 (E. coli O157:H7NR) in blanched spinach and to evaluate model performance with an independent set of data for interpolation (8.5, 13, 15 and 27 °C) and for extrapolation (broth and fresh-cut iceberg lettuce) using the ratio method and the acceptable prediction zone method. The lag time (LT), specific growth rate (SGR) and maximum population density (MPD) obtained from each primary model were modeled as a function of temperature (7, 10, 17, 24, 30, and 36 °C) using Davey, square root, and polynomial models, respectively. At 7 °C, the populations of E. coli O157:H7NR increased in tryptic soy broth with nalidixic acid (TSBN), blanched spinach and fresh-cut iceberg lettuce, while the populations of E. coli O157:H7 decreased in TSB after 118 h of LT, indicating the risk of nalidixic acid-resistant strain of E. coli O157:H7 contaminated in ready-to-eat produce at refrigerated temperature. When the LT and SGR models of blanched spinach was extended to iceberg lettuce, all relative errors (percentage of RE = 100%) were inside the acceptable prediction zone and had an acceptable Bf and Af values. Thus, it was concluded that developed secondary models for E. coli O157:H7NR in blanched spinach were suitable for use in making predictions for fresh cut iceberg lettuce, but not for static TSBN in this work.
Keywords: nalidixic acid-resistant E. coli O157:H7; blanched spinach; fresh cut iceberg lettuce; growth model
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MDPI and ACS Style

Kim, J.; Chung, H.; Cho, J.; Yoon, K. Evaluation of Models Describing the Growth of Nalidixic Acid-Resistant E. coli O157:H7 in Blanched Spinach and Iceberg Lettuce as a Function of Temperature. Int. J. Environ. Res. Public Health 2013, 10, 2857-2870.

AMA Style

Kim J, Chung H, Cho J, Yoon K. Evaluation of Models Describing the Growth of Nalidixic Acid-Resistant E. coli O157:H7 in Blanched Spinach and Iceberg Lettuce as a Function of Temperature. International Journal of Environmental Research and Public Health. 2013; 10(7):2857-2870.

Chicago/Turabian Style

Kim, Juhui; Chung, Hyunjung; Cho, Joonil; Yoon, Kisun. 2013. "Evaluation of Models Describing the Growth of Nalidixic Acid-Resistant E. coli O157:H7 in Blanched Spinach and Iceberg Lettuce as a Function of Temperature." Int. J. Environ. Res. Public Health 10, no. 7: 2857-2870.

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