Modeling the Inactivation of Intestinal Pathogenic Escherichia coli O157:H7 and Uropathogenic E. coli in Ground Chicken by High Pressure Processing and Thymol.

Shih-Yung Chien,Shiowshuh Sheen,Christopher H. Sommers,Lee-Yan Sheen

doi:10.3389/fmicb.2016.00920

Abstract

Disease causing Escherichia coli commonly found in meat and poultry include intestinal pathogenic E. coli (iPEC) as well as extraintestinal types such as the Uropathogenic E. coli (UPEC). In this study we compared the resistance of iPEC (O157:H7) to UPEC in chicken meat using High Pressure Processing (HPP) in with (the hurdle concept) and without thymol essential oil as a sensitizer. UPEC was found slightly more resistant than E. coli O157:H7 (iPEC O157:H7) at 450 and 500 MPa. A central composite experimental design was used to evaluate the effect of pressure (300–400 MPa), thymol concentration (100–200 ppm), and pressure-holding time (10–20 min) on the inactivation of iPEC O157:H7 and UPEC in ground chicken. The hurdle approach reduced the high pressure levels and thymol doses imposed on the food matrices and potentially decreased food quality damaged after treatment. The quadratic equations were developed to predict the impact (lethality) on iPEC O157:H7 (R2 = 0.94) and UPEC (R2 = 0.98), as well as dimensionless non-linear models [Pr > F (<0.0001)]. Both linear and non-linear models were validated with data obtained from separated experiment points. All models may predict the inactivation/lethality within the same order of accuracy. However, the dimensionless non-linear models showed potential applications with parameters outside the central composite design ranges. The results provide useful information of both iPEC O157:H7 and UPEC in regard to how they may survive HPP in the presence or absence of thymol. The models may further assist regulatory agencies and food industry to assess the potential risk of iPEC O157:H7 and UPEC in ground chicken.

Highlights

While most Escherichia coli are harmless, some are considered pathogenic for human beings that include both intestinal pathogenic E. coli as well as extraintestinal pathogenic E. coli (ExPEC)
In this study we report the development and validation of regression models for the inactivation of intestinal pathogenic E. coli (iPEC) O157:H7 and uropathogenic E. coli (UPEC) in chicken meat with by combining High Pressure Processing (HPP) and thymol for ground chicken
E. coli Cultures and Cocktail Preparation iPEC O157:H7 C9490, 59762, and 59768, and UPEC 700336, 700414, and 700415 (Sommers et al, 2016) were obtained from the American Type Culture Collection (Manassas Virginia)

Summary

Introduction

While most Escherichia coli are harmless, some are considered pathogenic for human beings that include both intestinal pathogenic E. coli (iPEC) as well as extraintestinal pathogenic E. coli (ExPEC). Escherichia coli O157:H7 are Shiga toxin-producing E. coli (STEC) are one type of iPEC which are common contaminants in meat and poultry (Bryan et al, 2015). HPP Lethality with Thymol on iPEC & UPEC on Meats outbreaks due to STEC were reported including recent ones at retail restaurants and wholesale outlets (chicken salad) [Centers for Disease Control and Prevention (CDC), 2015]. UPEC are common contaminants in poultry meat and other foods and cause infection after colonization of the gastrointestinal tract followed by accidental transfer of UPEC contaminated feces from the anus to the urethra (Jakobsen et al, 2010; Markland et al, 2015; Mitchell et al, 2015; Müller et al, 2016). While STEC are responsible for ca. 300 deaths in the US annually, the ExPEC are responsible for ca. 26,000, the percentage which could be attributed to contaminated food is currently unknown as there may be multiple routes for infection of humans by the ExPEC (Scallan et al, 2011; Nordstom et al, 2013; Singer, 2015)

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