Emerging Contaminants Summit

Spring 2020

StudentCompetitionHannah Gray
Graduate Student
Johns Hopkins University

Hannah Gray is a second-year PhD student studying Environmental Engineering at Johns Hopkins University in Baltimore, MD. She conducts her research at the Johns Hopkins Applied Physics Laboratory where she is investigating novel microfluidic systems for environmental microbiology. She completed her Bachelor’s and Master’s degree Environmental Engineering at the Viterbi School of Engineering at the University of Southern California in Los Angeles, CA. At Johns Hopkins, she is a participant in the NSF Integrative Education and Research Traineeship focused on innovation at the water-climate-health nexus.


Rapid Detection of Antimicrobial Resistance in Wastewater using a Novel Microfluidic Approach

Tracing the development of antimicrobial resistance and its spread from sources through wastewater treatment and into the environment is crucial for identifying the risks from contact with antimicrobial contaminants. However, existing analytical methods inadequately describe the extent, activity, and diversity of resistance. Conventional culture-based methods capture only a small percentage of bacterial diversity, require long isolation and incubation periods, and do not provide information about underlying mechanisms of physiological characteristics. Molecular methods like PCR fail to capture the extent of resistance and depend on existing knowledge of resistance genes and organisms of interest, preventing the analysis of novel genes and microbial species. A high-throughput microfluidic droplet system with the ability to encapsulate single bacterial cells at a rate of over 100,000 drops per minute may enhance identification, quantification, and back-end genetic analysis for ant imicrobial resistant bacteria. Each droplet, a few pico-liters in volume, is an isolated bioreactor with a single cell inoculum, enabling cell-by-cell experiments. Using this system, resistance to triclosan, a widely used and persistent antimicrobial compound, can be rapidly detected and quantified in wastewater. The droplet technique eliminates isolation steps during which significant bacterial diversity can be lost, while also reducing incubation periods for rapid results. Preliminary experiments demonstrate the feasibility of rapid Minimum Inhibitory Concentration Tests for antibiotics in a fraction of the conventional test time frame, and suggest that environmental bacterial isolation can generate an order of magnitude more organisms than classic plate methods. This project establishes the protocol for triclosan resistance detection during wastewater treatment.

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