High/Low Level Disinfection
Cleaning Studies
Steam/EO/Chemical Sterilization

High/Low-Level Disinfection Testing

Medical devices designed and labeled for reuse come in a wide variety of sizes, shapes, and internal/external configurations. It’s important to determine exactly what level of application is required to reliably disinfect a device after each use. Disinfection validation verifies the device manufacturer’s recommended disinfection parameters.

This work is a Microtest specialty. We have the knowledge, experience, specialized equipment and techniques, and strict adherence to protocols required for this demanding task.

The device is first inoculated with a biological challenge organism used as an indicator. Recommendations of the United States Pharmacopeia (USP) and Association for the Advancement of Medical Instrumentation (AAMI) suggest organisms with high resistance to the given sterilization process. The device is then disinfected, and tested for the indicator. If the indicator organism is still present, the device fails the test.

High-level disinfection requires a 6 log reduction of the inoculum, usually a mycobacterium species (Mycobacterium sp.). Low-level disinfection requires a 6 log reduction of the inoculum, often a series of indicators: the bacteria Pseudomonas aeruginosa (Ps. aeruginosa), the nasal carrier Staphylococcus aureus (S. aureus), and the bacteria Salmonella choleraesuis (S. choleraesuis) are often used as biological challenges.

Testing utilizes a 103-106 liquid spore suspension containing the indicators. Inoculated devices are cultured under an ISO Class 5 (Class 100) laminar airflow hood, using aseptic technique, determination of recovery factors, and traditional culture/enrichment techniques to optimize indicator recovery.

Test controls:

  • All culture media undergo USP Growth Promotion Testing (GPT) and sterility assurance to ensure optimal recovery and sterility
  • Incubators are calibrated and monitored 24/7 via an advanced SCADA system
  • Bacterial spore populations used in biological challenges are controlled and verified per USP prior to use, with the D-value of the indicator organism reported
  • Each sample is tested with positive and negative controls


Reusable Medical Device Disinfection and Cleaning Validation Requirements

Reusable medical devices have expensive components that require cleaning and disinfection. The FDA now requires additional information on 510(k) submissions that require clarity in the validation options offered to practitioners.

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