Instrument & test kit

The UroFAST pathogen ID/AST test comprises a software controlled plate reader, and a test kit. The test kit comprises 4 selective reagents implemented on 96 well plates and 150 mm Agar media plates for AST characterization.

The plate reader collects absorbance spectra from each well in a 96 well plate, in the wavelength range 390 to 830 nm. The software initiates data acquisition, and performs data analysis and report generation. UroFAST characterizes urine samples for presence, concentration and sub classification of common uropathogens, and for antimicrobial susceptibility characterization. Results are provided after 8 hours of testing and are meant to influence the choice of initial antibiotic therapy for patients with a urinary tract infection (UTI).

Functions

UroFAST provides an 8 hour test for urine samples, with results on

  1. Pathogen Presence
  2. Pathogen subclassification
  3. Concentration
  4. Antimicrobial susceptiblity

Comparison with other options

Currently, antimicrobial susceptibility testing is done after “bacteria isolation” steps that generally take 24+ hours, with the antimicrobial susceptibility testing itself taking another 24 hours.  These steps are required because the susceptibility metric (with conventional methods) is unreliable when non-standardized (or “poly-microbial”) test suspensions are used.  We have developed workarounds these issues, and are able to test the clinical sample directly.   Accordingly, we provide results at 8 hours (vs 48 hours required for conventional methods), at very similar price-points for the test kit, and reduced labor requirements.

Expected clinical impact

There are about 19M/year-US urine cultures, with about 7% positive1.  Overall, depending on the location, 9–31% of all cases of sepsis arise from an infection of the urogenital tract (urosepsis)2. As per a study by Talan and coworkers3, among ED patients hospitalized for UTI at 11 US centers, ~1/3 had sepsis, and ~¼ had a resistant strain (i.e., ESBL-producing Enterobacterales).  Of those with a resistant strain, more than half were not initially treated with an effective antibiotic.  A separate study by Talan and coworkers4 demonstrated that effectiveness of initial therapy correlates strongly with outcomes.  Thus, the UroFAST test is expected to improve Urosepsis outcomes.

  1. Cairns, C. & Kang, K. National Hospital Ambulatory Medical Care Survey: 2019 Emergency Department Summary Tables. https://stacks.cdc.gov/view/cdc/115748 (2022)
  2. Levy, M. M. et al. Outcomes of the Surviving Sepsis Campaign in intensive care units in the USA and Europe: a prospective cohort study. Lancet Infect. Dis. 12, 919–924 (2012)
  3. Talan, D. A. et al. Emergence of Extended-Spectrum β-Lactamase Urinary Tract Infections Among Hospitalized Emergency Department Patients in the United States. Ann. Emerg. Med. 77, 32–43 (2021)
  4. Talan, D. A. et al. Comparison of ciprofloxacin (7 days) and trimethoprim-sulfamethoxazole (14 days) for acute uncomplicated pyelonephritis pyelonephritis in women: a randomized trial. JAMA 283, 1583–1590 (2000)

Specifications

Parameter Specification
Time to result 8 hours (no pre-incubation required)
Limit of detection Demonstrated LOD of 1000 CFU/mL.
Limit of quantification and dynamic range Demonstrated LOQ of log CFU/mL =4, with a dynamic range of log CFU/mL between 4 and 10.  Sufficient to quantitate all urine infections.  Quantitation precision/accuracy is better than current methods.
Analytical sensitivity Demonstrated detection & sub classification of a broad range of microbial species at close to the limit of detection.
Analytical specificity Demonstrated that expected negative result is obtained for a broad range of microbial species for which a negative result is expected.
Microbial interference Expected positive results for the target species is obtained in the presence of high levels of non-target organisms
Interfering substances & Dilution 10x dilution of urine sample is sufficient to mitigate against most of the effects of the interfering substances
Contamination Demonstrated minimal (< 1/96) cross-contamination
Accuracy & Precision Demonstrated that accuracy/precision are sufficient to eliminate Very Major Errors VMEs for bacteria concentrations > 104 CFU/mL.
Repeatability Demonstrated that different UroFAST instruments provide substantially similar results
Bacteria presence and concentration in clinical samples Bacteria sub-classification and concentration results from UroFAST in clinical samples matches the results with plate counting methods.  R.m.s concentration difference is less than 1 (in log CFU/mL)
Antimicrobial susceptibility in clinical samples Antimicrobial susceptibility characterization by UroFAST matches the results with traditional (CLSI M2 standard) disk diffusion testing. Clinical performance metrics are detailed in Table 2
Metric Specification
Category Agreement CA 88% for Resistant, 44% for Intermediate & 91% for Susceptible
minor Error mE 13%
Major Error ME 3%
Very Major Error VME 0%

CA:  Both UroFAST and CLSI methods provide the same interpreted result (Resistant vs Intermediate vs Susceptible)

mE:  Either UroFAST or CLSI methods provides an Intermediate result, and the other one does not

ME:  CLSI methods indicate a Susceptible strain, but UroFAST indicates a Resistant Strain

VME:  CLSI methods indicate a Resistant strain, but UroFAST indicates a Susceptible Strain

Current Status

Available as Research Use Only.  FDA process started