Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: December 11, 2005
Publication Date: December 11, 2005
Citation: Chan, L., Han, R., Low, S., Tan, J., Bhagwat, A.A. 2005. Environmental adaptive mutations in diarrheagenic escherichia coli and their effect on infection dose. Proceedings of the US-Japan Cooperative Program in National Resources, Cherry, J. P. and Pavlath, A. E. (Eds.). p. 370-374.
Out of three distinct acid-resistance systems that have been identified in E. coli, the glutamate-dependent acid resistance system (GDAR) is believed to provide the highest protection from stomach acidity. In this study the acid-resistance systems of 82 foodborne outbreak strains of pathogenic E. coli isolated from 34 countries and 23 states within the U.S.A. were examined. Twenty nine isolates were found to be defective in inducing GDAR under aerobic growth conditions indicating they may be carrying mutant rpoS allelles. We took a physiological and recombinant DNA approach to confirm mutations in the rpoS genes, which may have been introduced during environmental adaptation. DNA sequence analysis, glycogen synthesis and heat-shock analysis revealed that there is heterogenity in the rpoS function, which had a profound influence on stress tolerance responses. Such mutations most likely alter infectivity of individual isolates and may play a significant role in determining the infective dose of diarrheagenic E. coli.