Wednesday, 6 November 2019

Update on disinfectant test standards

Two European disinfectant test standards have been updated this year.

EN 1276: 2019 Phase 2 / Step 1 – Quantitative Bactericidal Suspension Test

This involves at least two Gram-positive bacteria (Staphylococcus aureus and Enterococcus hirae) and at least two Gram-negative organisms (Pseudomonas aeruginosa and Escherichia coli), with the provision for additional test organisms if desired.

Incorporated into the test procedure are interfering substances to simulate clean and dirty conditions using different levels of Bovine Serum Albumin (BSA) and the effect of water hardness. Temperatures and contact times can be incorporated based on manufacturer’s recommendations.

Three disinfectant concentrations are included to cover the active and non-active range; this is to provide some control on the test method (i.e. the non-active concentration would be expected to fail the test). There are also additional controls to ensure that the test procedures are satisfactory, to demonstrate that the neutralisation procedure is effective and to ensure that the neutralisation agents do not themselves inactivate the test organisms.

The basic requirement is at least a 5-log reduction of all the test organisms.

This test is intended to take account of some of the environmental parameters (e.g. water hardness, organic load) as well as the effect of the contact time, all of which may influence the efficacy of the disinfectant under in-use conditions. However, it should be noted that ready to use disinfectants will be disadvantaged in comparison to concentrated disinfectants when tested according to this method, as some dilution is always produced by the addition of inoculum and interfering substance. Ready to use products can only be tested at a concentration of 97% or less.

EN 1650: 2019  Phase 2 / Step 1 - Quantitative Fungicidal Suspension Test

This test procedure serves a similar function to the Quantitative Bacterial Suspension Test (EN 1276) but is intended to cover fungicidal activity.

This test utilises the same two organisms as used in the Phase 1 Basic Fungicidal Test (Candida albicans and Aspergillus brasiliensis) with the provision for additional test organisms if desired. It incorporates the same interfering substances and test controls as in the Quantitative Bactericidal Suspension Test and has the same limitation regarding testing of ready to use products. The temperature and contact time are recommended by the disinfectant manufacturer.

The basic requirement is at least a 4-log reduction for all the test organisms . This requirement is less stringent than that required for the quantitative bacterial suspension test and reflects the expected reduced susceptibility of fungi to disinfectant preparations compared to bacteria.

Posted by Dr. Tim Sandle, Pharmaceutical Microbiology

1 comment:

  1. Perfect and well written article. Thank you Dr Tim.


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