To identify bloodstream pathogens and measure their antimicrobial susceptibility within hours using a single-cell analysis platform.
Approach:
Workflow Description: The system combined bacterial enrichment, fluorescence-based identification, and phenotypic antimicrobial susceptibility testing (AST).
Sedimentation-Assisted Enrichment: The first stage, STREAM, involved mixing whole blood with culture broth and dextran to separate bacteria from red blood cells.
Bacterial Identification: Molecularly barcoded sequential fluorescence in situ hybridization was used to identify individual bacteria by targeting bacterial 16S ribosomal RNA.
Susceptibility Testing: Bacteria were immobilized in agarose gel and exposed to antimicrobial concentrations, with time-lapse imaging used to measure changes.
Key Findings:
Results were produced in 6.75 to 17 hours for whole blood spiked with clinical bacterial isolates.
96% concordance with clinical laboratory identification in 104 positive blood culture samples.
98% essential agreement and 94% categorical agreement with clinical laboratory results for susceptibility testing.
4% very major error rate for resistant isolates misclassified as susceptible.
Interpretation:
The workflow demonstrated rapid identification and susceptibility testing of bloodstream pathogens, but further validation in clinical settings is needed.
Limitations:
Testing was conducted on spiked samples rather than actual patient blood.
Potential effects of prior antimicrobial exposure on bacterial recovery.
Faster-growing organisms may obscure additional pathogens in polymicrobial infections.
Intracellular, nonculturable, anaerobic, or fastidious organisms may require different processing conditions.
The multistep workflow requires specialized imaging and further automation.
Conclusion:
The study presents a promising method for rapid identification and susceptibility testing of bloodstream pathogens.
