Mikrobiologi

This standard describes the detection and isolation of Shiga toxin-producing Escherichia coli (STEC). The procedure includes the detection by Real Time PCR of the major virulence genes of STEC, stx1 and stx2 (Reference [2]) in enrichment cultures. Isolation of STEC from the enrichment culture is attempted if one or both stx genes are detected in the screening. This document is applicable to — products intended for human consumption, — products intended for animal feeding, — environmental samples in the area of food and feed production, handling, and — samples from the primary production stage.

This document is applicable to pure cultures of STEC. The present standard describes the characterization of STEC strains, isolated from any source. In particular, the characterization of STEC strains described here regard: - subtyping of the Stx-coding genes; - determination of the presence of eae gene; - determination of the presence of aggR gene; - identification of the presence of genes associated to the following serogroups: O157, O26, O111, O103, O145, O121 and O45. The full characterization of the isolated STEC strains is achieved by performing all the modules described here. The characterization scheme is not sequential, and the different modules can be implemented separately based on specific needs (e.g. Regulatory needs, Competent Authority’s requests, clients’ request). Alternative methods may be used, including Whole Genome Sequencing (WGS), provided these are verified according to the reference standard ISO 16140-2.

This part of ISO 10705 specifies the general principles for assessing the performance of methods for the concentration of bacteriophages from water. Concentration is recommended for those water samples expected to contain < 3 pfp (plaque-forming particles) per millilitre. Concentration methods can be applied to all kinds of water provided that the amount and nature of suspended solids and/or dissolved matter do not interfere with the concentration procedure. This part of ISO 10705 does not give specific details of concentration methods, but outlines the fundamental principles for evaluating the suitability of a particular method for a given type and volume of water. Annex A gives examples of methods that have been found satisfactory and their fields of application.