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The Scientific World Journal
Volume 2014, Article ID 135856, 6 pages
http://dx.doi.org/10.1155/2014/135856
Research Article

Influence of Sanitizers on the Lipopolysaccharide Toxicity of Escherichia coli Strains Cultivated in the Presence of Zygosaccharomyces bailii

1Unit for Applied Food Science and Biotechnology, Central University of Technology, Free State, P.O. Box 20539, Bloemfontein 9300, South Africa
2Fonterra Co-Operative Group Limited, Private Bag 11029, Palmerston North 4442, Dairy Farm Road 1, Palmerston North, New Zealand

Received 16 January 2014; Revised 6 May 2014; Accepted 7 May 2014; Published 25 May 2014

Academic Editor: Fernando Rodrigues

Copyright © 2014 Lerato Mogotsi et al. 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 influence of sublethal concentrations of two sanitizers, liquid iodophor and liquid hypochlorite (LH), on the growth rates and toxicity of food-borne pathogenic Escherichia coli strains grown in the presence of spoilage yeast Zygosaccharomyces bailii was assessed. When grown in combination with Z. bailii both E. coli O113 and E. coli O26 exhibited slower growth rates, except when E. coli O113 was grown in combination with Z. bailii at 0.2% LH. The growth rate of Z. bailii was not impacted by the addition of the sanitizers or by communal growth with E. coli strains. LAL and IL-6 results indicated a decrease in toxicity of pure E. coli cultures with comparable profiles for control and sanitizer exposed samples, although the LAL assay proved to be more sensitive. Interestingly, pure cultures of Z. bailii showed increased toxicity measured by LAL and decreased toxicity measured by IL-6. LAL analysis showed a decrease in toxicity of both E. coli strains grown in combination with Z. bailii, while IL-6 analysis of the mixed cultures showed an increase in toxicity. The use of LAL for toxicity determination in a mixed culture overlooks the contribution made by spoilage yeast, thus demonstrating the importance of using the appropriate method for toxicity testing in mixed microbe environments.