The information provided by certain tests is, however, of no value in identification because
the results given are always negative. These tests are as follows: in the API 20E strip - lysine
decarboxylase, ornithine decarboxylase and tryptophan deaminase; and in the API SOCHB
strips - erythritol, L-xylose, and L-arabitol. In addition, D-fuCoSe and 2-ketogluconate appear to
be of little value. This is a surprisingly small number of redundant tests considering that the
systems were originally designed for the identification of Enterobacteriaceae and other Gramnegative
rods. Several of the remaining tests appear to be of only moderate value because they
merely support the separation achieved using tests of high discriminatory value; such support is,
however, valuable in many cases because of the high within-species variation encountered in
several species.
For several species, fewer than ten strains were available for study and in these instances the
results in Table 1 are of reduced value for identification. In 25 species or groups, however, large
numbers of strains were available and the results are considered to give an adequate indication
of within-species variation (Sneath, 1978~; Gordon, 1981) for each test.
The results shown in Table 1 are most conveniently discussed by considering each species or
group separately.