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Abstract
SUMMARY: Members of the genus Aeromonas produced extracellular toxic antigens which were specific for this group and antisera produced against these antigens could be used to identify these organisms. Strains of A. liquefaciens, A. punctata, A. hydrophila and A. formicans were apparently very closely related; differences which existed between them were not greater than differences found among the strains of A. liquefaciens. Fresh isolates tended to be strongly haemolytic, produced extracellular toxins which were lethal to mice and elicited haemorrhagic lesions upon injection into the skin of rabbit. Old laboratory cultures tended to be much less haemolytic and less toxigenic. A. salmonicida appeared to possess extracellular antigens specific for this species but some strains of A. liquefaciens were found to possess this antigen.
Members of the genus Serratia were included in this study since Stevenson (1959) suggested that all Aeromonas strains are non-pigmented forms of Serratia. All strains of Serratia examined, regardless of their classification into species, were homogeneous and reacted with antiserum produced with one strain. Moreover, no cross-reaction was found between the antigens of Aeromonas and Serratia and it appeared unlikely that Aeromonas could be regarded as a non-pigmented member of Serratia. No cross-reaction was found between the extracellular antigens of these two genera and the other members of the families Enterobacteriaceae and Pseudo- monadaceae and antisera produced with these antigens appeared useful in the identification of Aeromonas and Serratia.
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