Overview
ISO 24072:2023 specifies an aerosol bacterial retention test method for assessing the bacterial retention ability of finished air‑inlet filters used on administration devices for infusion and transfusion applications. The method simulates a worst‑case aerosol challenge using a Staphylococcus aureus suspension to quantify bacteria that penetrate the filter under controlled laboratory conditions. Because the aerosol test is destructive and stringent, it is primarily intended for design verification and validation rather than routine production QC.
Key topics and technical requirements
- Challenge organism: Staphylococcus aureus ATCC 6538™ (or equivalent) prepared in TSB/NB and diluted in sterile saline.
- Aerosol generator parameters: target mass median aerodynamic diameter (MMAD) of (2.5 ± 0.5) µm and geometric standard deviation (GSD) ≈ 1.8; generator calibration per manufacturer.
- Flow and sampling: test flow set to 50 ml/min (flowmeter accuracy ±5 %), drawn by a vacuum pump; sampling duration and spraying time validated per test system.
- Validation: first‑use validation and revalidation after system changes; minimum of three runs to demonstrate a challenge level of 1.0 × 10^4 to 5.0 × 10^4 CFU collected in 30 min.
- Collection and analysis: use liquid impingers (bubblers) with sterile saline as collecting fluid, membrane filtration and culture on TSA/NA at (32.5 ± 2.5) °C for 18–24 h to enumerate CFU. An analytical filter membrane of nominal 0.45 µm is used for counting.
- Pass/fail criteria: test valid only if positive control meets the challenge range; sample passes when collecting fluid from the downstream impinger shows zero growth.
- Reporting: include sample specification, reference to ISO 24072:2023, method, results (with clause references), positive control result, deviations, unusual observations and date.
Applications and practical use
- Performance verification of stand‑alone and integrated air‑inlet filters on IV administration sets and transfusion devices.
- Design validation during device development and comparative testing between filter designs or suppliers.
- Regulatory and conformity documentation to demonstrate bacterial retention performance under aerosol challenge conditions that are stricter than typical clinical airborne loads.
Note: the standard highlights that aerosol testing is destructive and resource‑intensive, so it is not generally suited for routine lot‑by‑lot quality control.
Who should use this standard
- Medical device manufacturers (R&D, validation, QA) of infusion and transfusion administration devices.
- Independent testing laboratories and notified bodies performing performance evaluations.
- Regulatory and compliance teams preparing technical documentation for submissions.
Related standards
- ASTM F838‑20 (liquid bacterial retention tests), ASTM F2101‑19 (aerosol BFE for masks), ASTM F1671‑22 (liquid virus retention) - all cited for context in ISO 24072.
- ISO 8536‑4 for examples of air‑inlet filter assemblies referenced in the test apparatus description.
Keywords: ISO 24072:2023, aerosol bacterial retention test, air-inlet filter, administration devices, infusion, transfusion, Staphylococcus aureus, MMAD, liquid impinger, bacterial retention ability.
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