Evaluation of Salmonella Selective Media for Detecting H₂S Negative Salmonella Species

Abstract

We evaluated the most effective media for isolating hydrogen sulfide (H₂S) non-producing Salmonella. Hydrogen sulfide non-producing Salmonella is a common cause of of food poisoning and the incidence seems to be increasing. At present, it is popular to use medium for isolating Salmonella that is based on Salmonella spp. producing H₂S.
However, it is difficult to detect H₂S non-producing Salmonella and it is very easy to miss them. We evaluated several popular media in food testing using 27 strains of H₂S nonproducing Salmonella that were isolated from feces samples.
Many H₂S non-prpducing Salmonella were not detectable by traditional media nor Rambach Agar or Brilliant Green Agar. The latter two media do not depend on H₂S production.
A new chromogenic medium CHROMagar Salmonella (CHROMagar Ltd; France) uses a specific enzymatic reaction of Salmonella, and was able to distinguish all Salmonella colonies clearly irrespective of H₂S production, therefore, the CHROMagar Salmonella is very valuable in screening for Salmonella in food and environmental specimens. However, the media did not support the growth of Shigella and Salmonella Typhi and thus is not suitable for clinical specimens.
We believe that this chromogenic media should be widely used as isolating medium for the screening of Salmonella to increase the reliability of food sanitary control.