One of the major difficulties in the identification of Aeromonas
strains to species level concerns the current number of
recognized taxa (n 14) and the lack of clear-cut phenotypic
tables useful in distinguishing each of these groups from the
others (17). This problem has arisen because taxonomic studies
often report only selected biochemical characteristics on newly
described species and then compare these results to phenotypic
data from previously published studies on genetically
related taxa. Although the tests used may be the same in each
study, the growth conditions, medium composition, inoculation
procedure, and incubation conditions may vary considerably,
potentially affecting results (12, 15).
In some instances, commercial systems have been used to
generate the data, and it is not always clear how closely microidentification
test results parallel results obtained by conventional
methodology (2). Furthermore, many of the biochemical
schemes currently used in clinical laboratories to
identify aeromonads predate the description of newer taxa (1,
5, 7, 22). This fact calls into question whether previously selected
biochemical tests used to identify older Aeromonas species
are applicable to the identification of those described
more recently. Finally, the diversity in testing methodologies
has hampered the development of consistent phenotypic properties
and typing schemes with which to identify most Aeromonas
strains, if necessary, to species level in the clinical laboratory.
In this study we present cumulative biochemical data on
almost 200 Aeromonas strains representing each of the 14
recognized species and propose possible schemes for their
identification in the clinical laboratory (Table 1).