Characterization of "Pasteurella" piscicida isolated from white perch and cultivated yellowtail

The morphological, physiological, and biochemical characteristics of twelve "Pasteurella" piscicida strains isolated from white perch and yellowtail are described and the present uncertain taxonomic status of the organisms is discussed. The organisms isolated were gram-negative rods showing bipolar staining and pleomorphism. No spores or flagella were observed. They were non motile and viscid colonies were formed. Growth was observed in a temperature range of 20 to 30 C and the salinity range of growth was between 0.5% and 4.0%. They were aerobic and facultative anaerobic. Oxidase and catalase were produced. Nitrates were not reduced to nitrites. Lysine and ornithine decarboxylases were not produced but arginine dihydrolase was produced. The egg yolk reaction was positive. Tween 80 and tributyrin were decomposed. Phosphatase was produced. Beta hemolysis was revealed on a medium containing defibrinated blood from chickens or carp but not from mammals. Methyl red and Voges-Proskauer tests were positive, and acetoin was produced from 2,3-butanediol. Glucose was fermented without gas production. Acid was produced from fructose, mannose, galactose, sucrose, maltose, dextrin and glycerol. These organisms differed from all other members of the genus Pasteurella with respect to nitrate reduction, arginine dihydrolase, Voges-Proskauer and methyl red tests. The formation of viscid colonies and inability to grow in a medium without sodium chloride or at 37 C were additional characteristics of these organisms.