Scientific review: Cidália Pina Vaz
The importance of what happens before testing
When a blood culture becomes positive, clinical microbiology laboratories face an important challenge: recovering microorganisms suitable for downstream analysis.
Modern identification and antimicrobial susceptibility testing technologies can provide valuable information, but their performance depends partly on the characteristics of the material entering the analytical process.
Traditionally, laboratories obtain suitable microorganisms through subculture, allowing isolated colonies to develop before preparing suspensions for subsequent testing. Alternative preparation methods can recover microorganisms directly from positive blood cultures, potentially avoiding this additional incubation step.
However, an important question remains: does recovering bacteria necessarily mean they are immediately suitable for phenotypic susceptibility testing?
A study published on 1 October 2026 in Biomedical Microdevices provides new experimental evidence addressing this question. Researchers at the University of Southampton compared five blood-lysis protocols for isolating Escherichia coli and Staphylococcus aureus from positive blood-culture bottles.
Recovering bacteria is not the same as preserving their immediate activity
The researchers evaluated bacterial recovery, viability and sample quality using colony counting, optical flow cytometry and microfluidic impedance cytometry.
Although all five protocols recovered substantial numbers of organisms by conventional overnight colony counting, immediate measurements told a more nuanced story. The researchers observed that different preparation conditions could affect the immediate growth response of S. aureus, highlighting that bacterial recovery alone does not fully describe the suitability of a preparation method for rapid phenotypic testing.
The study also showed that residual blood cells and cellular debris can complicate bacterial enumeration. This matters because reliable inoculum preparation is an essential part of many phenotypic susceptibility workflows.
Why this matters for rapid phenotypic AST
MALDI-TOF identification and phenotypic antimicrobial susceptibility testing have different biological requirements.
MALDI-TOF identifies microorganisms primarily through their protein profiles and does not require the cells to remain metabolically active during identification. Phenotypic AST, by contrast, depends on viable microorganisms responding to antimicrobial exposure.
The Southampton researchers note that many rapid isolation chemistries were originally developed for mass-spectrometry identification rather than for downstream phenotypic AST. Their results illustrate why a preparation method that performs adequately for one application may not automatically be optimal for another.
For laboratories seeking to accelerate blood-culture workflows, sample preparation should therefore be assessed not only by how much bacterial material is recovered, but also by viability, sample cleanliness and suitability for the intended downstream method.
QUICKprep: designed around viable microbial recovery
At FASTINOV, the importance of microbial viability has been central to our work in rapid microbiology.
Our research into flow-cytometry-based antimicrobial susceptibility testing required microbial suspensions that preserved the biological characteristics necessary for downstream phenotypic analysis. This experience contributed to the development of QUICKprep.
QUICKprep is a manual sample-preparation kit designed to recover viable microorganisms directly from positive clinical samples. In approximately five minutes, the procedure produces a microbial pellet that can be resuspended and standardized to 0.5 McFarland for downstream identification and antimicrobial susceptibility testing procedures.
The process uses standard laboratory equipment and does not require a dedicated preparation instrument.
QUICKprep is not itself an identification or AST assay. Its role is to provide viable microbial material for downstream identification and antimicrobial susceptibility testing.
Sample preparation deserves a central role in rapid microbiology
As clinical microbiology continues to adopt faster analytical technologies, attention must extend beyond analytical speed.
Microbial recovery, viability, sample cleanliness and inoculum preparation all influence the development of reliable workflows. A preparation method suitable for identification alone may not necessarily meet the requirements of rapid phenotypic susceptibility testing.
At FASTINOV, we believe that rapid microbiology starts before the analytical instrument. QUICKprep addresses that upstream step by providing a simple approach to recovering viable microorganisms from positive clinical samples for downstream testing.
Reference
Tomás Cançado DN, Saito MS, Spencer D, Morgan H. Isolating viable bacteria from positive blood cultures: impedance cytometry analysis. Biomedical Microdevices. 2026;28:71. Published 1 October 2026.