This medium can be used as a screening method for the differentiation of Enterobacteriaceae based on the ability of some species to utilise citrate as a sole source of carbon. It is often used as a screening test for Klebsiella pneumoniae (Positive reaction) while Escherichia coli is negative. Other uses included distinguishing between species of citrate positive Salmonellae (e.g. Salmonella enteritidis) and those that are negative (e.g. Salmonella typhi and Salmonella paratyphi A). The medium is inoculated by stabbing the organism (in pure culture) into the medium. A positive result produces a change of colour from green to bright blue and a negative reaction leaves the colour unchanged.
Thiosulphate Citrate Bile Salts Sucrose (TCBS) Agar TCBS is a selective isolation medium for culture of pathogenic Vibrio spp. from clinical samples. The formulation was developed by Kobayashi, Enomoto, Skazaki and Kuwahara. This medium inhibits most enterobacteriacae for at least 24 hours. For the isolation of Vibrio spp. other than V.cholerae in environmental bacteriology, it is advisable to incubate at the lower temperature range of 20°C – 30°C. NB - It is not recommended to perform an oxidase test on any presumptive positive isolates directly from TCBS medium.