The key aspects are that the tubes fit properly, have flat optically clear bottoms, can be capped for mixing, and contain 1-3 mL volumes ideal for the densitometers.

There are a few options for tubes besides the proprietary biomerieux ampules:

• Glass or plastic flat-bottom test tubes (10-15mL) with screw caps can work. Ensure the tubes fit in the densitometer properly.
• Disposable plastic spectrophotometer cuvettes (1.5mL) may fit into some models. They are flat-bottomed and suitable for absorbance readings.
• Custom glass culture tubes can be made to fit specific models.
• Adapter racks are available to hold standard test tubes in certain densitometer models. This allows use of common 12-16mm tubes.
• Some users report reusing cleaned biomerieux ampules to save costs. However sterility may be a concern with this approach.

When preparing bacterial suspensions for use in bioMérieux densitometers, it's essential to use specialized test tubes that are compatible with the instrument's requirements. Typically, bioMérieux densitometers use disposable plastic cuvettes or tubes designed specifically for their systems.

These cuvettes or tubes are typically made of optical-grade plastic or glass to ensure accurate and consistent measurements. They are designed to fit securely into the instrument's sample chamber and are often pre-calibrated or manufactured with precise dimensions to maintain the integrity of the measurement.

Additionally, these cuvettes or tubes are typically sterile to prevent contamination of bacterial suspensions during testing. Sterility is crucial to obtaining accurate and reliable results.

In summary, when working with bioMérieux densitometers, it's advisable to use the dedicated cuvettes or tubes provided by the manufacturer. These are specially designed for compatibility with the instrument and to ensure the accuracy and sterility required for bacterial suspension measurements.

Maitham Ghaly Yousif Thank you for your time and dedication while writing your answer. Still, unfortunately, I didn't ask for the characteristics of biomerieux test tubes nor the role of sterility during work, because I am a microbiologist. I asked for substitutes for the original ampules.

Salah A. Alshehade Thanks for answering. Do you have some more information about these adapters? As you mentioned, there are multiple 10-15 mL tubes that fit biomerieux densitometers, but they are too high and because of that withdrawing liquid with automatic pipettes is impossible..