Comparison of Selective Media for Primary Isolation of Campylobacters
Many different types of selective media have been developed3–5, 7, 9, 11, 12. The foremost characteristic of an effective (“high performance”) plating media is the support of the growth of a wide range of C. jejuni strains with inhibition of the growth of other unwanted bacteria (background microbial flora). Background flora associated with Campylobacter is dependent upon the sample matrix2. Campylobacter-selective, high performance media were based on the ability of the media to recover the most campylobacters (“high, target signal”) with least colonization by background contaminants (“low, competitive signal. Plate counts are the scores of distinct values for colonization by Campylobacter (“target signal” C for Campylobacter percent recovery) versus colonization by flora (“competitive signal” F for flora percent recovery). The calculated test measure differential recovery% is differential recovery %=C − F(Eqn. 1). The ratiometric recovery is ratiometric recovery = C/(C+F) (Eqn. 2). The differential recovery% value approaching 100 represents overwhelming growth of Campylobacter in the presence of little or no flora. However this test measure may not resolve situations in which there is equivalent suppression of Campylobacter growth or enhancement flora colonization. The ratiometric measure used in tandem with the differential measure resolves this redundancy. Most of the trends in variation in the data were visualized using differential recovery% side-by-side range boxplots6,10.
KeywordsSelective Medium Milk Matrice Inoculation Level Ratiometric Measure Left Hand Quadrant
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