Michael Dodd University of Washington ? Seattle
The prevalence of antibiotic resistance traits has increased dramatically amongst bacterial populations within health-care settings during the last several decades. Concurrently, it has also become clear that antibiotic resistant bacteria (ARB) and their associated antibiotic resistance genes (ARGs) are widely distributed within aquatic environmental systems (e.g., municipal wastewaters, agricultural waste streams, and even treated drinking waters). Within this context, the use of disinfectants (i.e., chemical or physical agents applied to aqueous matrixes or inanimate surfaces) and antiseptics (i.e., chemical or physical agents applied to living tissues) to inactivate ARB present in water supplies, in municipal wastewater, or on contaminated surfaces can provide a critical means for mitigating dissemination of antibiotic resistance. However, even if ARB are fully inactivated during disinfection processes, intact segments of their ARG-containing DNA may remain within the resulting cell debris and confer antibiotic resistance traits to temporally- or spatially-separated bacterial populations by means of horizontal gene transfer processes not requiring live DNA donor cells, such as natural transformation. This research project is being undertaken to: (a) quantify the likelihood of intact, biologically-active ARGs ?surviving? disinfection processes even after ARB inactivation, and (b) to provide the data necessary to evaluate and mitigate risks posed by such ARGs in promoting dissemination of antibiotic resistance amongst environmental and clinically-relevant bacterial communities. A suite of conventional and molecular microbiological analytical tools will be utilized to examine the fate of free (extracellular) and cell-associated (intracellular) chromosomal and plasmid-borne ARGs from a variety of bacterial species during exposure to the disinfectant and antiseptic agents most commonly applied in water treatment and health-care settings. The results obtained from these investigations will enable quantitative modeling of extracellular and intracellular ARG deactivation during disinfection processes currently applied in water treatment and health-care practice, in turn making it possible to design disinfectant and antiseptic applications specifically for deactivation of ARGs.
This work will provide the first systematic investigation into the use of disinfectant and antiseptic agents expressly for the degradation and deactivation of ARGs. The resulting data will not only facilitate optimization of disinfection processes for minimizing the transfer of intact ARGs amongst natural and engineered aquatic environments and health-care settings, but will also greatly improve fundamental understanding of DNA reactivity toward various disinfectants and antiseptics and the mechanisms by which bacterial cells are inactivated during disinfection processes. Because of high public awareness as to the societal importance of antibiotic resistance, this topic also represents an exceptional opportunity to engage K-12 teachers and students in strengthening STEM curricula. The project will therefore be utilized as a platform from which to partner with groups of STEM teachers and underrepresented students from regional high schools, in order to develop suites of instructional laboratory modules focusing on concepts relevant to the project scope. These laboratory modules will subsequently be implemented within regional high school curricula, as well as utilized by the PI to aid in the training of new undergraduate and graduate research assistants. The project will also support the career development of a graduate student and several underrepresented undergraduate students.
