No Proteus? No Problem!
In 1968, Hektoen Enteric (HE) Agar was introduced by the Hektoen Institute of Chicago. HE agar is a selective and differential agar used for the culture of Salmonella and Shigella from patient stool samples. HE agar contains indicators of lactose fermentation and hydrogen sulfide production, while possessing inhibitors to prevent the growth of Gram-positive bacteria.
Unfortunately, HE agar also allows for the growth of Proteus, which can lead to an abundance of false positives for Salmonella. It is because of this that Proteus has been given the name the “Great Imposter.” Proteus spp. are Gram-negative, saprophytic Proteobacteria and are therefore abundant in stool cultures. Many microbiologists over the years found themselves working “through the noise” that Proteus presented to try and find Salmonella cultures on traditional HE plates.
In 2012, Hardy Diagnostics introduced HardyCHROM™ SS agar which was a chromogenic selective and differential medium for the detection and cultivation of Salmonella and Shigella. The color differentiation on the plate was meant to help labs save time through the color identification of the different species of bacteria. H2S producing Salmonella would appear as large clear colonies with black centers while non-H2S producing Salmonella and Shigella would show as teal colonies. However, the problem of Proteus still persisted.
Four years later the Research and Development Manager at Hardy Diagnostics, Alani Vasquez, made a brilliant discovery. While working on the development of a new product, she discovered a new compound with activity specifically against Proteus spp. This compound was added to the HardyCHROM™ SS NoPRO to eliminate the Proteus spp. colonies which is non-pathogenic in stool cultures.
Due to her observation, HardyCHROM SS NoPRO has easily revolutionized how we test for Salmonella and Shigella. With its outstanding sensitivity and specificity, HardyCHROM™ SS NoPRO saves time and money by eliminating the need for the lab staff to work up suspect Salmonella and Shigella only to find out, after much time and expense, it is only Proteus.
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