Improved Positive Predictive Performance of <i>Listeria</i> Indicator Broth: A Sensitive Environmental Screening Test to Identify Presumptively Positive Swab Samples

PDX-LIB, Listeria Indicator Broth, was developed as a proprietary sensitive screening test to identify presumptively positive environmental swab samples for Listeria sp. The original formulation, while sensitive, initially proved to exhibit acceptable levels of false positive test results. Paradigm Diagnostics has been undertaken to modify the medium formulation to render it more selective while not sacrificing its sensitivity. After identification of a candidate formulation through laboratory studies, a field trial was conducted to validate the test performance parameters, including the true positive frequency and false positive frequency in several different food-processing facilities. Identical swab samples were enriched in both the original medium formulation and the new formulation. Presumptive positive samples were confirmed by plating on selective differential agar and qPCR analysis. The field trial data demonstrate that the new formulation significantly reduces the frequency of false positive samples compared to the original Listeria Indicator Broth formulation, without compromising the sensitivity of the original formulation. The new medium formulation resulted in no false positive samples compared to the 54% increased presumptive positive samples obtained with the original medium formulation

Toledean testimony: Reconquista, architectural Convivencia and the man from La Mancha

This is how the discovery occurred. One day I was in the Alcana at Toledo, when a lad came to sell some parchments and old papers to a silk merchant. Now as I have a taste for reading even torn papers lying in the streets, I was impelled by my natural inclination to take up one of the parchment books the lad was selling, and saw in it characters which I recognized as Arabic. But though I could recognize them I could not read them. Don Quixote de la Mancha-(Graf, 1999, p. 77)