Response and defense mechanisms of extraintestinal escherichia coli to reactive oxygen and chlorine species - members of the escherichia coli species are remarkably diverse and comprise commensal,…

The National Institute of Allergy and Infectious Diseases awarded the Board of Trustees of Illinois State University $555,000 on June 17, 2026, under the Allergy and Infectious Diseases Research program (CFDA 93.855) to investigate the response and defense mechanisms of extraintestinal Escherichia coli to reactive oxygen and chlorine species.

The research examines how extraintestinal pathogenic E. coli strains defend against bactericidal host defense mechanisms, specifically reactive oxygen and chlorine species such as hypochlorous acid generated during neutrophil-mediated phagocytosis and by uroepithelial cell enzymes. The principal investigator's prior work identified the RcrR regulon, consisting of RcrA and RcrB genes and controlled by the RCS-sensing transcriptional repressor RcrR, as responsible for increased resistance to reactive oxygen and chlorine species in extraintestinal E. coli compared to non-pathogenic and enteropathogenic strains. The funded research will characterize the precise mechanism of RcrB function and the role of RcrA and other potential defense mechanisms during reactive oxygen and chlorine species stress, with the long-term goal of increasing the efficacy of existing antimicrobial approaches against extraintestinal E. coli infections. This work addresses the rising threat of antibiotic-resistant E. coli infections in humans and supports improved infection prevention and treatment strategies.

Performance occurs in Normal, Illinois, with an anticipated completion date of May 31, 2029.

Response and defense mechanisms of extraintestinal escherichia coli to reactive oxygen and chlorine species - members of the escherichia coli species are remarkably diverse and comprise commensal, probiotic and pathogenic strains. While some pathogenic e. Coli cause intestinal diseases, extraintestinal e. Coli (expec) can colonize and infect environments outside the GUT. For instance, members of this pathotype can inhabit the urinary tract where they are confronted with a multitude of bactericidal host defense strategies, which requires specialized genetic adaption for survival. Expec must defend highly toxic antimicrobials such as hypochlorous acid (hocl), a potent reactive oxygen and chlorine species (RO/CS) generated during neutrophil-mediated phagocytosis and by enzymes in uroepithelial cells to control bacterial colonization. The increasing rate of expec infections in humans due to changing infection dynamics demonstrate the critical need for a better understanding of expec pathogenesis, which is desperately needed to improve approaches for infection prevention and treatment given the rise in antibiotic resistance spreading among e. Coli. Our lab has reported that members of the expec pathotype are more resistant to RCS in vitro and to neutrophil-mediated phagocytosis when compared to non-pathogenic and enteropathogenic e. Coli. We identified the defense system responsible for these phenotypes and characterized its regulation during RCS stress: the rcrr regulon consisting of the rcrarb genes is controlled by the RCS-sensing transcriptional repressor rcrr, which reversibly loses its repressor activity upon oxidation by RCS, resulting in DE-repression of its downstream targets. Induced expression of rcrb contributes significantly to expec's increased RCS resistance, however, the precise mechanism of rcrb and the role of rcra (and potentially other defense players) during RCS stress remain enigmatic. Our long-term goal is to increase the efficacy of existing antimicrobial therapies by purposefully and selectively sensitizing expec to clearance by innate immune cells. The overall objective of this application is a comprehensive analysis of expec's RCS defense with particular focus on the mechanism of the rcrr regulon. We hypothesize that rcrb directly protects cells from hocl, while rcra, another member of the rcrr regulon, mediates evasion from hocl and invasion into host cells. In aim 1, we will use phenotypic, biochemical, and imaging approaches to investigate the mechanism by which rcrb contributes to expec's increased RCS resistance. In aim 2, we will study the role of rcra for expec motility, biofilm formation, and host cell invasion. In aim 3, we will use independent unbiased and targeted approaches, including phenotypic characterization of transposon mutants, to fully comprehend expec-specific responses to and defenses against RCS. Identifying, characterizing and targeting expec-specific defense systems has the potential to increase the body's own capacity to fight utis. Overall, we will involve at least four undergraduate students in our research projects, which we believe will provide an excellent training opportunity for the next generation of scientists.