Abstract
A total of 12 strains of the genus Aeromonas were all good producers of so-called caseinate precipitating enzyme (CP-enzymes). CP-enzymes produced by different Aeromonas species have been serologically compared. The technique is a special immuno-electro-phoretic procedure, in which the proteolytic activity is neutralized by specific antiserums. No intergeneric cross-reactions could be demonstrated between enzymes produced by members of the genera Aeromonas, Pseudomonas, Proteus and Aerobacter. Interspecies cross-reactions occurred between enzymes of Aeromonas salmonicida and the species Ae. liquefaciens, Aa. punctata and Ae. hydrophila, whereas CP-enzymes of Ae. proteolytica were not found to be serologically related to those of the other species of the genus. However, the liquefaciens–punctata–hydrophila group could be enzymo-serologically differentiated from Ae. salmonicida, because that group in addition to the common enzyme fraction also possesses a fraction not found in Ae. salmonicida. The enzymo-serological procedure has been found a convenient tool in the identification of Ae. salmonicida and other aeromonads.