Urea hydrolysis test was done using the method of Seeliger (1956).
The cultures were grown on Sabouraud agar and were transferred
to fresh slants before the urea test was done. Fresh cultures from
the slants were transferred with a loop to the surface of Christensen
urea medium consisting of the following: 0.1 g peptone; 0.1 g
glucose; 0.5 g NaCl; 0.2 g KH2PO4; 1.5 g agar and 0.012 g phenol
red per 1000 ml of distilled water. The ingredients were mixed and
melted in a water bath. After adjusting the pH to 6.8, the medium
was dispensed into test tubes in 4.5 ml amounts and autoclaved for
10 min at 121°C. The tubes were allowed to cool to 50°C. To every
tube of the autoclaved medium, 0.5 ml of a 20% Seitz-filtered
solution of urea was added aseptically. After mixing with the base,
the contents of the tubes were allowed to solidify with a long slant
and a deep butt. The inoculated tubes were incubated at the
optimal temperature (28 to 30°C) of the organism for 72 h. Urea
hydrolysis was indicated by a distinct colour change of the indicator
from a deep pinkish red to an orange-yellow colour starting at the
slanted part of the medium and progressing rapidly to the deep part
of the butt.