Numerical taxonomy and biochemical identification of fish associated motile Aeromonas spp.

Four hundred and thirty-right Aeromonas, 31 Vibrio and 3 Plesiomonas strains isolated from moribund and healthy fish, water samples and humans, including 36 reference strains, were compared using numerical taxonomy based on 128 unit characters. Data were examined by the simple matching (S-SM) and Jaccard (S-J) coefficients, and by unweighted average linkage clustering. As expected, Aeromonas spp. were clearly distinct from those of Vibrio and Plesiomonas. The motile Aeronomas spp., i. e. Aeromonas hydrophila, Aeromonas caviae and Aeromonas veronii biotype sobria formed discrete homogeneous clusters, distinct from the nonmotile species Aeromonas salmonicida. Furthermore, A. caviae was divided into two biotypes with D-mannose fermentation as the most important differentiating characteristic. Of the recently described species, A. veronii biotype veronii (type strain ATCC 35624) was phenotypically closest 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 cluster 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 predominating (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%).