Toprak Lab

Fast antibiotic susceptibility testing is the missing feedback loop in antibiotic stewardship. We build workflows that turn a blood sample into a quantitative MIC readout in hours—without giving the pathogen a two-day head start: isolate the microbe without waiting for culture amplification, then measure growth with optical sensitivity near the single-cell limit.

Rapid Pathogen Isolation from Blood

Pull the pathogen out of blood in minutes, not days.

Comparison of conventional 18–48 hour bacterial isolation versus rapid ~30 minute protocol from blood samples
Rapid bacterial isolation. Conventional culture-based workflows require 18–48 hours before susceptibility testing can begin (Panel A). A rapid protocol recovers bacteria directly from whole blood in approximately 30 minutes using standard laboratory equipment (Panel B), removing the culture amplification bottleneck.
Frontiers in Microbiology 2025

A simple, low-cost, and highly efficient protocol for rapid isolation of pathogenic bacteria from human blood

F.S. Coskun, J. Quick, E. Toprak

Frontiers in Microbiology 16:1637776 (2025)

A simple protocol that recovers viable pathogens directly from whole blood in ~30 minutes using standard lab equipment. In validation experiments it achieved >70% recovery efficiency, remained effective at very low bacterial loads, and preserved growth dynamics—so susceptibility testing can start immediately instead of after overnight culture.

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Ultrasensitive Optical Detection

Read growth from as few as ~20 bacterial cells.

RUSD platform schematic showing hollow fiber as optical waveguide and growth chamber, with laser, fiber, and photodiode components, calibration curve, and cell-size sensitivity heatmap
RUSD: a fiber that doubles as incubator and sensor. A hollow fiber acts as both growth chamber and optical waveguide. Light loss from scattering reports cell density with nearly four orders of magnitude higher sensitivity than standard OD reads, down to ~20 bacterial cells.
iFAST time-resolved dose-response heatmaps showing rapid MIC determination for multiple bacterial species and antibiotics
MICs as a time series. iFAST leverages RUSD sensitivity to infer MICs within hours. The time-resolved heatmaps show susceptibility boundaries emerging early, long before a standard culture would reach an OD readable by a plate reader.
PLOS Biology 2019

Rapid ultrasensitive detection platform for antimicrobial susceptibility testing

Mehmet F. Cansizoglu, Yusuf Talha Tamer, Michael Farid, Andrew Y. Koh, Erdal Toprak

PLOS Biology 17(5): e3000291 (2019)

A label-free optical platform that detects extremely low cell densities (down to ~20 bacterial cells) and enables MIC measurements in 2–4 hours across multiple pathogens and antibiotics. The goal is simple: keep the workflow familiar, but make the readout fast.

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From Bench Prototype to Rapid AST

Engineering the optics for robustness, dynamic range, and a clinic-friendly workflow.

Growth curves and heatmap of E. coli under varying cefepime concentrations in RUSD device, showing MIC determination at 45 minutes
MIC in under one hour. A redesigned portable RUSD instrument with temperature-stabilized optics achieves definitive cefepime MIC determination within 45 minutes. The growth heatmap shows clear dose-dependent separation, with sub-MIC concentrations producing detectable growth at the earliest time points.
Frontiers in Bioengineering and Biotechnology 2022

Label-Free Optical Detection of Pathogenic Bacteria and Fungi at Extremely Low Cell Densities for Rapid Antibiotic Susceptibility Testing

Michael Farid, Marinelle Rodrigues, Robert England, Erdal Toprak

Frontiers in Bioengineering and Biotechnology 10:884200 (2022)

Extends RUSD into a more robust apparatus with a wide dynamic window for bacterial and fungal detection and rapid dose-response measurements. In iFAST assays, growth separation can be visible within ~45 minutes and MIC boundaries can be interpreted on the order of an hour—without labels or specialized reagents.

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