AUTHOR=Elhadidy Mohamed , Álvarez-Ordóñez Avelino 

TITLE=Diversity of Survival Patterns among Escherichia coli O157:H7 Genotypes Subjected to Food-Related Stress Conditions

JOURNAL=Frontiers in Microbiology

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2016.00322

DOI=10.3389/fmicb.2016.00322

ISSN=1664-302X

ABSTRACT=<p>The purpose of this study was to evaluate the resistance patterns to food-related stresses of Shiga toxin producing <italic>Escherichia coli</italic> O157:H7 strains belonging to specific genotypes. A total of 33 <italic>E</italic>. <italic>coli</italic> O157:H7 strains were exposed to seven different stress conditions acting as potential selective pressures affecting the transmission of <italic>E</italic>. <italic>coli</italic> O157:H7 to humans through the food chain. These stress conditions included cold, oxidative, osmotic, acid, heat, freeze-thaw, and starvation stresses. The genotypes used for comparison included lineage-specific polymorphism, Shiga-toxin-encoding bacteriophage insertion sites, clade type, <italic>tir</italic> (<italic>A255T</italic>) polymorphism, Shiga toxin 2 subtype, and antiterminator <italic>Q</italic> gene allele. Bacterial resistance to different stressors was calculated by determining <italic>D</italic>-values (times required for inactivation of 90% of the bacterial population), which were then subjected to univariate and multivariate analyses. In addition, a relative stress resistance value, integrating resistance values to all tested stressors, was calculated for each bacterial strain and allowed for a ranking-type classification of <italic>E. coli</italic> O157:H7 strains according to their environmental robustness. Lineage I/II strains were found to be significantly more resistant to acid, cold, and starvation stress than lineage II strains. Similarly, <italic>tir</italic> (<italic>255T</italic>) and clade 8 encoding strains were significantly more resistant to acid, heat, cold, and starvation stress than <italic>tir</italic> (<italic>255A</italic>) and non-clade 8 strains. Principal component analysis, which allows grouping of strains with similar stress survival characteristics, separated strains of lineage I and I/II from strains of lineage II, which in general showed reduced survival abilities. Results obtained suggest that lineage I/II, <italic>tir</italic> (<italic>255T</italic>), and clade 8 strains, which have been previously reported to be more frequently associated with human disease cases, have greater multiple stress resistance than strains of other genotypes. The results from this study provide a better insight into how selective pressures encountered through the food chain may play a role in the epidemiology of STEC O157:H7 through controlling the transmission of highly adapted strains to humans.</p>