Harlequin® Chromogenic Agar for Salmonella Esterase (CASE) is a selective chromogenic agar for the detection of Salmonella, part of Neogen’s One Broth One Plate for Salmonella (OBOP-S) and ISO 6579-1:2017 workflow. Neogen’s OBOP-S workflow has been validated according to ISO 16140-2 and certified by both MicroVal and AOAC.

It is not intended to diagnose diseases or other conditions in humans.

CASE utilizes a dual chromogenic system to differentiate between Salmonella and non-target organisms that grow on the agar. The first chromogen is a target for esterase activity present in all Salmonella species and results in blue/green colonies. The second chromogen is a target for β-glucosidase activity, present in non-target organisms that are able to grow on the agar and also possess esterase activity. Utilization of the second chromogen masks the presentation of the first, resulting in black colonies in non-Salmonella organisms. All other organisms are either inhibited or grow colorless on the agar. The medium contains an opacity agent that provides a white background, facilitating easy reading and identification. The media can detect non-motile Salmonella (S. Pullorum and S. Gallinarum) as well as monophasic variants (1,4,[5],12:i:-). The media can also detect serovars that traditionally present weak esterase activity (S. Dublin) and lactose-positive strains (S. Arizonae). According to ISO 6579-1:2017, subculture is performed separately from both Rappaport-Vassiliadis medium with Soya (RVS broth) and Muller-Kauffmann tetrathionate-novobiocin (MKTTn) broth.