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Antimicrobial Efficacy Testing

 

SMTL test the antimicrobial activity of a range of medical devices and formulations using national and international standards. Whilst these standards recommend using particular test conditions, alternatives may be used at the request of the client or by recommendation from SMTL.

For products where standard methods may not be appropriate or cannot be used, SMTL have a strong background in developing bespoke test methods for clients thus ensuring that the testing is tailored for the product.

Several standard methods are available and can be categorised as either quantitative methods (results reported as a log reduction or percentage reduction) or qualitative methods (results usually reported as reduced growth, zones of no growth).

 

Quantitative Methods

 

Wound Dressings

SMTL have been testing the antimicrobial properties of wound dressings for over 20 years, some of that work has been published. SMTL staff have been involved in the development of the European standard (BS EN 17854) for the antimicrobial testing of wound dressings.

The standard specifies the minimum requirements and test method for the antimicrobial (microbicidal or microbistatic) activity of wound dressings. It applies to all wound dressings that specifically claim antimicrobial activity according to the standard. The standard aims to simulate conditions of application by using appropriate conditions that reflect the parameters found in clinical situations.

 

References

  • S.Thomas, P.McCubbin, A comparison of the antimicrobial effects of four silver- containing dressings on three organisms J. Wound Care 2003; 12; 3, 101-107
  • S.Thomas, P. McCubbin, An in vitro analysis of the antimicrobial properties of 10 silver- containing dressings J. Wound Care 2003; 12; 8, 305-308

 

Non-leaching, antimicrobial-treated specimens

Standard Test Method for determining the antimicrobial activity of immobilised antimicrobial agents under dynamic contact conditions.

ASTM E2149 is a quantitative test method which is used to measure the antimicrobial activity of materials (for example textiles and hard surfaces) treated with non-leaching (non-water soluble) antimicrobial agents. The ASTM E2149 test, known as the shake flask method, allows the testing of products of different shapes and sizes. Standard conditions specify a contact period of 1 hour using Escherichia coli.

 

Textile Products

BS EN ISO 20743 specifies quantitative methods to determine the efficacy of antimicrobial treatments on textiles. The standard gives the choice of three different methods. The client can select the most suitable method depending upon the nature and intended application of the product. Standard conditions specify a contact period of 24 hours using Staphylococcus aureus and Klebsiella pneumoniae.

BS EN ISO 20743 is equivalent to JIS L 1902 and AATCC 100.

 

Non-porous Materials

BS EN ISO 22196 specifies a quantitative method to determine the efficacy of antibacterial treatments on plastics and other non-porous materials, Standard conditions specify a contact period of 24 hours using Staphylococcus aureus and Escherichia coli.

BS EN ISO 22196 is equivalent to JIS Z 2801.

 

Qualitative Methods

 

BS EN IS0 20645

Textile fabrics. Determination of antibacterial activity. Agar diffusion plate test.

BS EN ISO 20645 is essentially a qualitative test method for determining the effect of antibacterial treatments applied to woven, knitted and other flat textiles, although semi- quantitative information can be obtained when comparing different concentrations of the same product. A minimum diffusion of the antibacterial treatment into the test agar is necessary with the procedure. The method is not suitable for testing materials treated with antimicrobials that react with the agar. Standard conditions specify a contact time period of 18-24 hours using Staphylococcus aureus and either Escherichia coli or Klebsiella pneumoniae.

pertidish antibac test

 

AATCC Test Method 147

Antibacterial Activity Assessment of Textile Materials: Parallel Streak Method.

The parallel streak method is a qualitative method to detect the antibacterial activity of diffusible antimicrobial agents on textile materials. The standard organisms are Staphylococcus aureus and Klebsiella pneumoniae. This method is particularly useful for thin woven materials.

If you have a product you wish to have tested or have any questions, please contact smtl.info@wales.nhs.uk

 

Relevant Standards

  • BS EN 17854 - Antimicrobial wound dressings. Requirements and test method
  • ASTM E2149 Standard Test Method for determining the antimicrobial activity of immobilised antimicrobial agents under dynamic contact conditions.
  • BS EN ISO 20743 Textiles - Determination of antibacterial activity of textile products
  • BS EN ISO 22196 Measurement of antibacterial activity on plastics and other non- porous surfaces
  • BS EN ISO 20645 Textile fabrics. Determination of antibacterial activity. Agar diffusion plate test
  • AATCC TM 147 Antibacterial Activity of Textile Materials: Parallel Streak
  • JIS L 1902 Determination of Antibacterial Activity of Antibacterial Finished Products (Textiles)
  • AATCC 100 Test Method for Antibacterial Finishes on Textile Materials
  • JIS Z 2801 Test for Antimicrobial Activity of Plastics