ISO INTERNATIONAL STANDARD 21528-2 Secondedition 2017-06 Microbiology of the food chain : Horizontal method for the detection and enumeration of Enterobacteriaceae - Part 2: Colony-count technique Microbiologie de la chaine alimentaire - Méthode horizontale pour larechercheetledénombrementdesEnterobacteriaceae Partie 2: Techniquepar comptage des colonies Reference number ISO 21528-2:2017(E) os1 International Organization for Standardization @ IS0 2017 HEJIANG INST OF STANDARDIZATION C1 5956617 ed without license from IHS IS0 21528-2:2017(E) COPYRIGHTPROTECTEDDOCUMENT IS0 2017, Published in Switzerland All rights reserved. Unless otherwise specified, 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 on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISO's member body in the country of the requester. ISOcopyrightoffice Ch. de Blandonnet 8 . CP 401 CH-1214 Vernier, Geneva, Switzerland Tel. +41 22 749 01 11 Fax +41 22 749 09 47 [email protected] www.iso.org Internatinair PrganizationforStandardization ensee-ZHEJIANG INST OF STANDARDIZRoISQ $17 - All rights reserved Not for Resale, 2017/9/12 02:53:05 etworking permitted without license from IHS IS0 21528-2:2017(E) Contents Page Foreword ..iv Introduction. ..V 1 Scope. .1 2 Normative references ..1 3 Terms and definitions ..1 4 Principle .2 4.1 Preparation of initial suspension and decimal dilutions .2 4.2 Isolation and selection for confirmation .2 4.3 Confirmation. .2 4.4 .2 Calculation 5 Diluent, culture media and reagent ..2 6 Equipment and consumables ..2 7 Sampling. .3 8 Preparation of test sample ..3 9 Procedure .3 9.1 General .3 9.2 Test portion, initial suspension and dilutions .4 9.3 Inoculation and incubation 4 9.4 Counting and selection of colonies for confirmation .4 9.5 Subculturing selected colonies. 4 9.6 Biochemical confirmation tests .5 9.6.1 Oxidase reaction 5 9.6.2 Fermentationtest .5 9.6.3 Interpretation of biochemical tests .5 10 Expression of results .5 11 Performance characteristics of the method. .5 11.1 Interlaboratory study ..5 11.2 Repeatability limit. .5 11.3 Reproducibility limit .6 12 Test report .6 13 Quality assurance .7 Annex A (normative) Culture media and reagents Annex B (informative) Method validation studies and performance characteristics ..12 Bibliography .15 iii withoutlicense from IHS