Epidemiological Correlates of Virulence Genotype and Phylogenetic Background among Escherichia coli Blood Isolates from Adults with Diverse-Source Bacteremia

Associations of virulence genotype and phylogenetic background with epidemiological factors (primary source of bacteremia, host compromise status, and hospital versus community origin) were assessed among 182 Escherichia coli blood isolates from adults with diverse-source bacteremia in comparison with fecal controls from the E. coli Reference collection. A continuum of virulence was found, from urinary and pulmonary source bacteremia isolates (high virulence), through "other" or unknown source bacteremia isolates (intermediate virulence), to fecal isolates (low virulence), with a corresponding graded phylogenetic distribution from predominantly group B2 to predominantly groups A and B1. Associations of bacterial traits with clinical factors varied considerably, depending on subgroup and statistical method. However, certain putative virulence genes (including several "nontraditional" markers, such as pathogenicity island-associated malX) repeatedly emerged as significant epidemiological predictors, which provided evidence of their possible relevance in host-pathogen interactions and hence as potential targets for preventive interventions against extraintestinal infections due to E. coli.