28-Quantitative Method for Evaluating Bactericidal Efficacy of Biocides Used on Hard Surfaces

https://www.oecd.org/chemicalsafety/testing/44162951.pdf 

Quantitative Method for Evaluating Bactericidal Efficacy of Biocides Used on Hard Surfaces 

DRAFT OECD GUIDELINE FOR THE TESTING OF CHEMICALS

SUMMARY 

1. This method uses disks (1 cm in diameter) of brushed stainless steel as default carrier to represent hard, non-porous environmental surfaces. Each disk receives 10 L of the test organism in a soil load. The inoculum is dried and exposed to 50 L of the use-dilution of the test substance; control carriers receive an equivalent volume of a fluid harmless to the test organism. The contact time and temperature may vary as required. A neutralizer is added at the end of the contact time and the disks then eluted. Most or all of the eluate volume from each disk is assayed for the presence of viable organisms. Log10 or percentage reductions in the viability of the test organism are calculated in relation to the viability titre on the control carriers.

INTRODUCTION 

Background and Scope 2. This Test Guideline is designed for testing the bactericidal activity of substances to be used on hard surfaces Springthorpe and Sattar 2005 (1), (2). Assessments of microbicidal activity using carrier tests give a better indication of the potential of a given microbicide to perform under field conditions. International harmonisation of test methodology has been developed from meetings (OECD 2002) (3), reports and ongoing national and international initiatives that mandate such testing be quantitative in nature, and has agreed upon performance criteria. Performance criteria may vary depending on the intended use and label claim of the product. Data from such testing can also provide a basis for classification and labelling of a tested formulation. Statistical techniques are employed to ensure data validity. This test has evolved as a modification of a previous standard of ASTM International (2006) (4) following significant international collaboration among OECD member states. A ring trial to validate five new antimicrobial efficacy methods including this one was carried-out from 2007 to 2009 in which thirty-five laboratories from eight member countries participated and a validation report (5) was produced. 3. Definitions used in this Test Guideline are given in Annex I. Prerequisites for test substance 4. The following information on the test substance should be known before the start of testing: 1) The physical state of test substance, its trade name or identification number (ID), lot number(s), source and receipt date at the testing laboratory. 2) Chemical nature and relative concentrations of microbicidal ingredients if available; such information may come from product label or manufacturer’s safety data sheet 

Enterococcus hirae (ATCC 10541) 20. 

For this test organism, the culture medium should be prepared as follows: - prepare a soybean-casein digest broth - add 100 µL of stock culture to 10 mL of broth and incubate for 18 h – 24 h at 36±1°C to obtain 1.5 108 CFU/mL to 5.0 108 CFU/mL. 5 - Prior to inoculation of carriers, the soil load should be aseptically added. -Soybean-casein digest agarshould be used as Post-Exposure Recovery Medium -......

REFERENCES 

(1) Springthorpe, V.S. and Sattar, S.A. (2005a). Quantitative Carrier Tests to Assess the Microbicidal Activities of Chemicals: Rationales & Procedures. ISBN 0-88927-298-0, Centre for Research on Environmental Microbiology (CREM), Univ. of Ottawa, Ottawa, ON, Canada. 100 pages. Available from QCTmanual@webbertraining.com. 

(2) Springthorpe, V.S. and Sattar, S.A. (2005b). Carrier tests to assess microbicidal activities of chemical disinfectants for use on medical devices and environmental surfaces. J. AOAC International 88: 182-201. 

(3) OECD (2002). Report of the Efficacy Workshop on Certain Antimicrobial Biocides, Arlington, VA, U.S.A., OECD meeting held in April 2002. 

(4) ASTM International (2006). Standard Quantitative Disk Carrier Test Method for Determining the Bactericidal, Virucidal, Fungicidal, Mycobactericidal and Sporicidal Activities of Liquid Chemical Germicides. Method E-2197-02, Vol. 11.05. ASTM International, West Conshohocken, PA, U.S.A.

 (5) OECD (2009). Report on validation of efficacy methods for antimicrobials used on hard surfaces 

(6) DeVries, T. A. and Hamilton, M.A (1999). Estimating the antimicrobial log reductions: Part 1: Quantitative assays. Quant. Microbiol. 1: 29-45. 

(7) Sharpe, A. N. and Peterkin, P. I. (1988). Membrane Filter Food Microbiology. John Wiley & Sons, New York, NY.