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Routine control of culture media in accredited laboratory for food microbiology

Quality control of culture media in accredited microbiological laboratory according to the standard HRN EN ISO / IEC 17025 is implemented in accordance with the standard HRN CEN ISO / TS 111333-2 - Guidelines on preparation and production of culture media – Part 2: Practical guidelines on performance testing of culture media. In laboratories carrying out microbiological examination of food, the main objectives are to maintain, resuscitate, grow, detect and/or enumerate a wide variety of microorganisms. Culture media meeting established or minimal performance criteria are prerequisite for any reliable microbiological work. Sufficient testing should be carried out to demonstrate: a) the acceptability of each batch of medium ; b) that the medium is "fit for purpose" ; and c) that the medium can produce consistent results. These three criteria are an essential part of internal quality control procedures and, with appropriate documentation, permit effective monitoring of culture media contribute to the production of both accurate and precise data. The aim of this research was to describe procedures for control of culture media, which are important factor in ensuring quality of laboratory work in food microbiology. All media produced in laboratory are controlled by reference strain of microorganism. Apart from the growth of target microorganisms, selectivity of the culture media is examined, meaning if it can suppress the growth of the non-target microorganisms. The control of culture media includes physical-chemicals parameters and microbiological quality criteria: pH value, appearance, volume, moisture content, productivity, selectivity, sterility and specificity. After several years of performing solid media control, the best results have been achieved by the modified Miles-Misra technique which is the simplest and the most suitable for calculation of productivity ratio and for estimation selectivity. Qualitative control of liquid media productivity is based on determination of growth of the least possible number of microorganisms. This paper demonstrates control of culture media in practice and its documentation.

Quality control; HRN EN ISO / IEC 17025; food microbiology

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