Four hundred and thirty-right Aeromonas, 31 Vibrio and 3 Plesiomonas s
trains isolated from moribund and healthy fish, water samples and huma
ns, including 36 reference strains, were compared using numerical taxo
nomy based on 128 unit characters. Data were examined by the simple ma
tching (S-SM) and Jaccard (S-J) coefficients, and by unweighted averag
e linkage clustering. As expected, Aeromonas spp. were clearly distinc
t from those of Vibrio and Plesiomonas. The motile Aeronomas spp., i.
e. Aeromonas hydrophila, Aeromonas caviae and Aeromonas veronii biotyp
e sobria formed discrete homogeneous clusters, distinct from the nonmo
tile species Aeromonas salmonicida. Furthermore, A. caviae was divided
into two biotypes with D-mannose fermentation as the most important d
ifferentiating characteristic. Of the recently described species, A. v
eronii biotype veronii (type strain ATCC 35624) was phenotypically clo
sest to A. hydrophila, although from DNA:DNA hybridisation studies it
was classified within the A. sobria group. Aeromonas schubertii (type
strain ATCC 43 700) was well defined and formed a single member cluste
r The phenotypic boundaries of Aeromonas media (type strain ATCC 33907
) and Aeromonas eucrenophila (type strain CDC 0859-83) were not clear.
All the fish isolates (n = 208) were identified, with A. hydrophila p
redominating (43.8%), followed by A. veronii biotype sobria (26.9%), A
. caviae biotype I (16.3%), A, salmonicida (6.7%), A, sobria (HG7) (2.
9%), A. caviae biotype II (2.4%), and A. veronii biotype veronii (1%).