Fine ceramics (advanced ceramics, advanced technical ceramics) — Determination of bacterial reduction rate by semiconducting photocatalytic materials under indoor lighting environment — Semi-dry method for estimating antibacterial activity on the actual environmental bacteria contamination surface

This document establishes a test method for determining the antibacterial activity of materials containing an indoor-light-active photocatalytic material on the surface. The antibacterial reduction rate is determined by measuring the survival of bacteria after illumination with indoor light. This test assumes a surface with high potential of possible person contact with bacteria. This test is designed to evaluate the suppression of contact infection of bacteria using an indoor-light-active photocatalytic material under indoor lighting environment. It is intended for use with different kinds of indoor-light-active photocatalytic materials used in construction, for example, flat sheets, board or plate shapes, which are the basic forms of materials for various applications. It is not applicable to powder, granular, or porous indoor-light-active photocatalytic materials, as well as cloths or textiles. It is applicable to indoor-light-active photocatalytic materials produced for antibacterial application. Other types of indoor-light-active photocatalytic materials applications, i.e. decomposition of water contaminants, self-cleaning, antifogging, and air purification, are non-applicable by this method.

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Status
Published
Publication Date
06-Jan-2020
Technical Committee
Current Stage
6060 - International Standard published
Start Date
07-Jan-2020
Completion Date
07-Jan-2020
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ISO 22551:2020 - Fine ceramics (advanced ceramics, advanced technical ceramics) -- Determination of bacterial reduction rate by semiconducting photocatalytic materials under indoor lighting environment -- Semi-dry method for estimating antibacterial activity on the actual environmental bacteria contamination surface
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INTERNATIONAL ISO
STANDARD 22551
First edition
2020-01
Fine ceramics (advanced ceramics,
advanced technical ceramics) —
Determination of bacterial reduction
rate by semiconducting photocatalytic
materials under indoor lighting
environment — Semi-dry method
for estimating antibacterial activity
on the actual environmental bacteria
contamination surface
Reference number
ISO 22551:2020(E)
ISO 2020
---------------------- Page: 1 ----------------------
ISO 22551:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

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below or ISO’s member body in the country of the requester.
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Published in Switzerland
ii © ISO 2020 – All rights reserved
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ISO 22551:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 2

5 Materials ....................................................................................................................................................................................................................... 2

5.1 Bacteria strains and preparation for tests ...................................................................................................................... 2

5.1.1 Bacteria strains ................................................................................................................................................................. 2

5.1.2 Subculture of bacteria strains............................................................................................................................... 3

5.2 Chemicals and implements .......................................................................................................................................................... 3

5.2.1 Dispersion medium for Staphylococcus epidermidis ......................................................................... 3

5.2.2 Dispersion medium for Escherichia coli ....................................................................................................... 3

5.2.3 1/5-concentration nutrient broth medium (1/5 NB) ...................................................................... 3

5.2.4 1/2-concentraion luris-bertani broth medium (1/2 LB).............................................................. 3

5.2.5 Nutrient agar medium (NA medium) ............................................................................................................. 4

5.2.6 Soybean-casein digest broth with lecithin and polysorbate 80 (SCDLP medium) . 4

6 Apparatus ..................................................................................................................................................................................................................... 4

7 Test piece ...................................................................................................................................................................................................................... 5

8 Procedure..................................................................................................................................................................................................................... 5

8.1 Preparation of test bacterial solution .................................................................................................................................. 5

8.1.1 Culturing of test bacteria .......................................................................................................................................... 5

8.1.2 Preparation of test bacterial solution ............................................................................................................ 5

8.2 Application of test bacterial solution ................................................................................................................................... 5

8.2.1 Measurement of test piece mass ........................................................................................................................ 5

8.2.2 Application of test bacterial solution ............................................................................................................. 5

8.2.3 Direct application method ....................................................................................................................................... 5

8.3 Indoor lighting condition ............................................................................................................................................................... 6

8.3.1 Measurement of luminance and preparation of setting position of test pieces ........ 6

8.3.2 Light exposure time ........................................................................................................................................... ............ 6

8.3.3 Test pieces inoculated with test bacterial solution under light condition ..................... 6

8.3.4 Test pieces inoculated with test bacterial solution under dark condition ..................... 6

8.4 Measurement of number of living bacteria .................................................................................................................... 7

8.4.1 Washout of inoculated bacteria .......................................................................................................................... 7

8.4.2 Measurement of bacterial concentration in washout solution ................................................ 7

8.4.3 Measurement of bacterial concentration in test bacterial solution ..................................... 7

9 Calculation .................................................................................................................................................................................................................. 8

9.1 General ........................................................................................................................................................................................................... 8

9.2 Test requirement fulfilment validation .............................................................................................................................. 8

9.3 Calculation of reduction rate of living bacteria ........................................................................................................... 9

10 Test report ................................................................................................................................................................................................................10

Bibliography .............................................................................................................................................................................................................................12

© ISO 2020 – All rights reserved iii
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ISO 22551:2020(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 206, Fine ceramics.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2020 – All rights reserved
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ISO 22551:2020(E)
Introduction

This document applies to testing the antibacterial activity of indoor-light-active photocatalytic

ceramics and other materials, produced by either coating or mixing of a light-active photocatalyst

in a simulated indoor lighting environment. The International Standard for testing the antibacterial

activity of photocatalytic materials has been published as ISO 27447 and the International Standard for

testing the antibacterial activity of indoor-light-active photocatalytic materials has been published as

ISO 17094.

Recently, it was discovered that antibacterial activities by indoor-light-active photocatalyst showed

different results between the ISO 17094 testing in a laboratory and the evaluation in a real environment.

Thus, the ISO 17094 testing method should be complemented by a testing method that simulates an

indoor lighting environment.

ISO 17094 is one of the best methods for measuring the potential of antibacterial activity using

photocatalysts. This document can measure the reduction rate of living bacteria by testing with impure

substances similar to an indoor lighting environment.
© ISO 2020 – All rights reserved v
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INTERNATIONAL STANDARD ISO 22551:2020(E)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Determination of bacterial reduction rate by
semiconducting photocatalytic materials under indoor
lighting environment — Semi-dry method for estimating
antibacterial activity on the actual environmental bacteria
contamination surface

WARNING — Handling and manipulation of microorganisms that are potentially hazardous

requires a high degree of technical competence. Only personnel trained in microbiological

techniques should carry out tests.
1 Scope

This document establishes a test method for determining the antibacterial activity of materials

containing an indoor-light-active photocatalytic material on the surface. The antibacterial reduction

rate is determined by measuring the survival of bacteria after illumination with indoor light. This test

assumes a surface with high potential of possible person contact with bacteria. This test is designed

to evaluate the suppression of contact infection of bacteria using an indoor-light-active photocatalytic

material under indoor lighting environment.

It is intended for use with different kinds of indoor-light-active photocatalytic materials used in

construction, for example, flat sheets, board or plate shapes, which are the basic forms of materials for

various applications. It is not applicable to powder, granular, or porous indoor-light-active photocatalytic

materials, as well as cloths or textiles.

It is applicable to indoor-light-active photocatalytic materials produced for antibacterial application.

Other types of indoor-light-active photocatalytic materials applications, i.e. decomposition of water

contaminants, self-cleaning, antifogging, and air purification, are non-applicable by this method.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 14605, Fine ceramics (advanced ceramics, advanced technical ceramics) — Light source for testing

semiconducting photocatalytic materials used under indoor lighting environment

ISO 17094:2014, Fine ceramics (advanced ceramics, advanced technical ceramics) — Test method for

antibacterial activity of semiconducting photocatalytic materials under indoor lighting environment

3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
© ISO 2020 – All rights reserved 1
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ISO 22551:2020(E)
3.1
photocatalyst

substance that performs one or more functions based on oxidization and reduction reactions under

photoirradiation, including decomposition and removal of air and water contaminants, deodorization,

antibacterial, antifungal, self-cleaning and antifogging actions
3.2
indoor-light-active photocatalyst

photocatalyst (3.1) that functions under illumination with artificial light used for general lighting

purposes
3.3
indoor lighting environment

illumination with artificial light source(s) used for general lighting purposes and excluding sunlight

3.4
indoor-light-active photocatalytic material

material in which or on which the indoor-light-active photocatalyst (3.2) is added by, for example,

coating, impregnation or mixing
3.5
reduction rate of living bacteria

reduction of the viable bacteria counts on the surface of indoor-light-active photocatalytic materials

(3.4) versus that of non-treated materials after treatment under illumination or in a dark condition for

a designated time, expressed as a proportion of the bacteria in percentage per unit of inoculating mass

3.6
dispersion medium

medium used for the preparation of a test bacterial solution, comprising a chemical component, which

simulates human sebum
4 Principle

The testing method is used to obtain the antibacterial activity of indoor-light-active photocatalytic

materials under indoor lighting condition by contact of a test piece with bacteria suspended in a

dispersion medium simulating human sebum. This method is applicable to materials with smooth

surfaces, such as flat sheet, board or plate-shaped materials.

The surface of the test piece is uniformly inoculated with bacterial suspension. The inoculated test piece

is placed on a Petri dish and a glass plate is placed on top of the Petri dish. The Petri dish containing

the test piece is exposed to light. After exposure, the test bacteria are washed out of the test piece. This

washout suspension is measured by the viable bacterial count method.
5 Materials
5.1 Bacteria strains and preparation for tests
5.1.1 Bacteria strains

The bacterial strains to be used in the test shall be the same as or equivalent to those described in

Table 1 and supplied by an entry registered under the World Federation for Culture Collections or the

Japan Society for Microbial Resources and Systematics.
2 © ISO 2020 – All rights reserved
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ISO 22551:2020(E)
Table 1 — Bacteria strains to be used in the test
Bacteria species WDCM code
Staphylococcus epidermidis WDCM 00132
Escherichia coli WDCM 00012
5.1.2 Subculture of bacteria strains

Testing is performed in a biosafety level testing room equipped for the required type of microorganisms

to be used. A nutrient agar slant medium (NA slant medium) is inoculated with Staphylococcus

epidermidis or Escherichia coli and streak cultured for 24 h to 48 h at (37 ± 1) °C. The cultured bacteria

can be stored at 5 °C to 10 °C for one month. Using this material as a stock strain, the cultured bacteria

can be subcultured up to 10 times under the same conditions.

NOTE 1 For long-term storage such as cryopreservation, appropriate measures are taken.

NOTE 2 If the activity of used bacteria is maintained, agar plates can be used.
5.2 Chemicals and implements

The chemicals, materials and implements used in this testing are as follows, unless otherwise

designated. The commercial media of the same components described below can be used.

5.2.1 Dispersion medium for Staphylococcus epidermidis

Add 49 ml of sterile water and 50 g of weighed triol-type polypropylene glycol (alpha, alpha', alpha''-

1,2,3-propanetriyltris [omega-hydroxy-poly[oxy(methyl-1,2-ethanediyl)]], average molecular weight

300 (PPG 300)) to a flask with a magnetic stirring bar. Immediately after addition, stir with the bar.

Then, add 1 g of polyethylene glycol [average molecular weight 500 000 (PEG 500K)] under continuous

stirring, and stir for 1 h. Sterilize in an autoclave at (121 ± 2) °C for at least 15 min. After dissolving,

use sodium hydroxide or hydrochloric acid to adjust the solution pH to (7,1 ± 0,2) at 25 °C. Adjust to

100 ml using sterile water. Sterilize in an autoclave at (121 ± 2) °C for at least 15 min and store at room

temperature. Do not use dispersion medium made more than one month previously.
5.2.2 Dispersion medium for Escherichia coli

Add 30 ml of sterile water and 0,1 g of weighed mucin to a flask with a magnetic stirring bar. Immediately

after addition, stir with the bar. Then, add 0,2 g of sodium alginate under
...

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