A recent application approved by FDA enables microbiologists to perform rapid sterility tests, obtaining results as fast as 90 min. This is a stunning advance in the microbiology field, since traditional sterility tests take 14 days until completion. Scan RDI Analyzer is an ultra-rapid microbial control of filterable products, what means that in addition to rapid sterility tests, it is possible to analyze water, bioburden, non-sterile products, environmental control, etc.

The system has a very high sensitivity, down to 1 cell per sample. It is possible to perform a rapid sterility test in your sample if its presumable total count is lower than 105 cells of bacteria and 104 cells of yeasts and molds.

Scan RDI Analyzer turns rapid sterility tests a reality by directly detecting and counting cells of bacteria, yeasts and molds, without the requirement of cell multiplication. In order to do so, it makes use of two technologies: fluorescent cell labeling and laser scanning, and is also called Solid-Phase Cytometry.

Rapid Sterility Test Procedure

1. Filter samples through a 0.4 µm pore size membrane. Microorganisms are retained.
2. Transfer the membrane to absorbent pads saturated with an activation reagent for 60 minutes.
3. Label samples with a specific reagent system, for 30 minutes.
4. Transfer the membrane to the analyzer, which uses a high-speed laser scanning system and scans all the surface of the membrane in three minutes.

The specific reagents employed to cell labeling uses enzymatic cleavage of a non-fluorescent substrate to liberate free fluorochrome into the cytoplasm.  Only viable cells, with intact cell membrane, are able to retain the fluorescent probe, what represents a significant advance if compared to ATP technologies, for example.

The signals originated from the analyzer are expressed as discrimination parameters on the screen, enabling the rapid sterility testing equipment to differentiate between labeled bacteria and interference signals, like electronic, optical or non-fluorescent particles. Since the entire process is non-destructive, it is possible to use a microscope to check and confirm that the labeled cell is really from a microorganism and not from any other organic particle.

Some studies have already shown that rapid sterility tests with Scan RDI is reliable, since it detects and counts all viable microorganisms in a sample, including spores, anaerobes, stressed or fastidious organisms.  In addition, the system is also capable of perform bacteria identification of Escherichia coli, Legionella pneumophila and also identifies Cryptosporidium and Giardia.

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