Salmonella Esterase Agar
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Chromogenic Salmonella Esterase Agar
A chromogenic agar for the detection of Salmonella spp. in clinical samples.
Chromogenic Salmonella Esterase (CSE) agar is a modified base agar containing peptones and nutrient extracts and incorporates the novel PPR esterase substrate. The growth of Salmonella spp. on this agar results in the hydrolysis of the ester to produce a brightly coloured phenol that remains within the colonies. This reaction is also dependent upon the presence of sugars and other energy substrates present in the medium. After 24 hours incubation at 37 or 42°C colonies of typical Salmonella species are burgundy coloured on a transparent yellow background whereas non-Salmonella species are white, cream, yellow or transparent.
In evaluation studies, CSE agar had a sensitivity of 93.1 %; this compares favourably with other commercially available chromogenic Salmonella agars (Rambach, 82.8 %; XLD, 91.4%; Hektoen-enteric, 89.7 %; and SM ID, 91.4 %. The CSE agar is particularly suitable for the detection of the more common Salmonella serotypes i.e. S. typhimurium and S. enteriditis that account for 85 % of the serotypes reported to the U.K. Public Health Laboratory Service (PHLS).
S. indiana and S. choleraesuis are not detected on CSE agar and some S. arizonae strains are only weakly coloured. However these strains give a false colour reaction on the Rambach and SM ID agars and although XLD and Hektoen-enteric are able to identify S. arizonae, they are unable to detect certain other serotypes. Those strains that are weakly or not detected on CSE agar are only rarely reported to the UK, PHLS (<0.3 %).
