# Using combinations of single-cell phenotypes for rapid antibiotic susceptibility testing

> **NIH NIH R43** · PHAST CORPORATION · 2020 · $300,000

## Abstract

Project Summary/Abstract
The fight against antibiotic resistance, one of the most pressing healthcare concerns worldwide, will require an
all-of-the-above approach, with one important element being the development of innovative rapid diagnostics.
PhAST Corp. has developed a new antibiotic susceptibility testing (AST) approach that has promise to
significantly accelerate AST, from tens of hours to tens of minutes. It is based on the quantification of
changes in single-cell pathogen phenotypes upon antibiotic exposure through single-cell, time-lapse
imaging. By systematically using multiple single-cell phenotypes, either individually or in combination, the
method is broadly applicable to a wide range of pathogens. Initial data obtained with reference strains, clinical
isolates and direct patient samples have revealed clear phenotypic changes consistently within 15–90 min of
antibiotic exposure, a considerable reduction over the many hours or days typically required by current
approaches. Importantly, the PhAST diagnostic platform works directly from patient samples, entirely
bypassing the time-consuming isolation and growth step that can last 1-2 days in gold standard assays and is
still required also in all recently developed rapid AST approaches. The goal of this project is to develop and
extensively validate PhAST's direct-from-sample approach, focusing on urinary tract infections (UTIs), one of
the most common bacterial infections associated with significant morbidity and healthcare costs due to the
high rates of antibiotic resistance.
The work will be structured around two aims, focusing on (Aim 1) validating PhAST with reference strains
and clinical isolates, in order to develop a mathematical model that determines susceptibility from
changes in single-cell phenotypes; and (Aim 2) validating PhAST using a large set of direct patient
urine samples. Our initial focus will be on the first and second line UTI treatment options, including
nitrofurantoin, trimethoprim/sulfamethoxazole and ciprofloxacin, though the method applies broadly to
antibiotics of all mechanisms of action. The approach will provide both qualitative results (susceptible /
intermediate / resistance categorization) and quantitative results (Minimum Inhibitory Concentration or MIC
determination). Performance will be evaluated by comparison with the gold-standard broth microdilution
method to obtain categorical agreement, essential agreement and error rates (minor / major / very major
errors). The proposed work will in particular include extensive testing with resistant strains, including multi-drug
resistant strains.
Ample preliminary data on a wide range of pathogen-antibiotic combinations and direct patient urine
samples has contributed to significantly de-risk the use of this new and potentially transformative
method for AST, paving the way for its extensive validation for the case of UTIs, proposed here. A successful
outcome of the proposed work will be the ability to obtain...

## Key facts

- **NIH application ID:** 9984961
- **Project number:** 5R43AI145769-02
- **Recipient organization:** PHAST CORPORATION
- **Principal Investigator:** Kwangmin Son
- **Activity code:** R43 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $300,000
- **Award type:** 5
- **Project period:** 2019-08-01 → 2021-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9984961

## Citation

> US National Institutes of Health, RePORTER application 9984961, Using combinations of single-cell phenotypes for rapid antibiotic susceptibility testing (5R43AI145769-02). Retrieved via AI Analytics 2026-05-27 from https://api.ai-analytics.org/grant/nih/9984961. Licensed CC0.

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