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ISOLATION OF CLOSTRIDIUM TETANI FROM SOIL.

Sanada, Ichiro (Kanazawa University, Kanazawa, Japan), and Shoki Nishida. Isolation of Clostridium tetani from soil. J. Bacteriol. 89:626-629. 1965.-The higher the temperatures applied to soil specimens, the weaker the toxigenicity of Clostridium tetani strains isolated from them. The glucose- and maltose-fermenting ability of these isolates was inversely proportional to their toxigenicity. The biological properties of atoxic strains were indistinguishable from those of C. tetanomorphum. Since a considerable number of toxic strains fermented glucose and maltose, these criteria are of doubtful value for differentiating C. tetani from C. tetanomorphum.

Antitoxins↗

TAXONOMY OF PSEUDOMONAS PISCICIDA (BEIN) BUCK, MEYERS, AND LEIFSON.

Hansen, A. J. (University of Idaho, Moscow), O. B. Weeks, and R. R. Colwell. Taxonomy of Pseudomonas piscicida (Bein) Buck, Meyers, and Leifson. J. Bacteriol. 89:752-761. 1965.-Twenty strains of marine bacteria showing the properties of pigmentation and icthyotoxicity were studied for selected physiological features. A quantitative taxonomic analysis with an electronic computer was performed. Eighteen species of Pseudomonas were included in the computer analysis as reference strains. The marine collection formed a homogeneous cluster, 80% similarity, and showed a 67 to 70% similarity to certain of the Pseudomonas species: P. atlantica, P. geniculata, P. synxantha, and P. taetrolens. The marine strains are treated as a phenon describing the species P. piscicida. The species was characterized by the hypothetical Median Organism concept; P. piscicida 14 corresponded most closely to the Median Organism.

Anti-Bacterial Agents↗

DETECTION OF UROCANASE IN THE BLOOD OF CHICKENS CHRONICALLY POISONED WITH TOXIC GROUNDNUT MEAL.

Chickens were fed for up to six weeks a ration containing 30 per cent of toxic groundnut meal and their controls were fed balanced commercial ration for comparable periods. Urocanase activity was determined in the blood and livers of principal and control birds killed after two, four or six weeks on these diets. Urocanase activity was detected in the blood sera of 3 out of the 9 intoxicated birds examined as early as two weeks after the initiation of the feeding trial. By the sixth week, the incidence of urocanase in the serum increased to 5 of 8 intoxicated birds. Liver urocanase concentration was uniform throughout the duration of the experiment when measured in units per gram of hepatic tissue. However, when its activity was expressed on the basis of units per total liver weight, its total activity increased toward the end of the experiment.

Aflatoxins↗

Molecular evolution of antibody affinity for sensitive detection of botulinum neurotoxin type A.

Botulism is caused by botulinum neurotoxin (BoNT), the most poisonous substance known. Potential use of BoNT as a biothreat agent has made development of sensitive assays for toxin detection and potent antitoxin for treatment of intoxication a high priority. To improve detection and treatment of botulism, molecular evolution and yeast display were used to increase the affinity of two neutralizing single chain Fv (scFv) antibodies binding BoNT serotype A (BoNT/A). Selection of yeast displayed scFv libraries was performed using methods to select for both increased association rate constant (k(on)) and decreased dissociation rate constants (k(off)). A single cycle of error prone mutagenesis increased the affinity of the 3D12 scFv 45-fold from a K(D) of 9.43x10(-10)M to a K(D) of 2.1x10(-11)M. Affinity of the HuC25 scFv was increased 37-fold from 8.44x10(-10)M to 2.26x10(-11)M using libraries constructed by both random and site directed mutagenesis. scFv variable region genes were used to construct IgG for use in detection assays and in vivo neutralization studies. While IgG had the same relative increases in affinity as scFv, (35-fold and 81-fold, respectively, for 3D12 and HuC25) higher solution equilibrium binding constants were observed for the IgG, with the 3D12 K(D) increasing from 6.07x10(-11)M to 1.71x10(-12)M and the HuC25 K(D) increasing from 4.51x10(-11)M to 5.54x10(-13)M. Affinity increased due to both an increase in k(on), as well as slowing of k(off). Higher affinity antibodies had increased sensitivity, allowing detection of BoNT/A at concentrations as low as 1x10(-13)M. The antibodies will also allow testing of the role of affinity in in vivo toxin neutralization and could lead to the generation of more potent antitoxin.

Antibody Affinity↗