CThe test aids in identification and
differentiation of enterobacteria. It is based on the
ability of an organism to utilize citrate as the sole
source of carbon and energy and ammonium salt as the
sole source of nitrogen for growth. Simmon’s citrate
agar slant was inoculated with large inoculums of the
isolate and incubated at 370C for 24hrs. Presence of
growth leads to the increase in turbidity and pH of the
medium resulting in the change of colour from green to
blue for positive reaction. Presence of the original green
colour indicates that citrate was not utilized and this
gives a negative reaction [4].