A Urease Test for the Differentiation of Brucella Suis

Abstract

During the study of the bacteriological characters of our Brucella cultures we observed that Brucelka suis could be easily distinguished from other Brucella species by means of the urease test, in a manner very similar to that used in the identification of Enterobacteriaceae. Our work was in progress when Culbertson's summary was published of the papers presented at the symposium on brucellosis that was held at Bethesda, Maryland, in September, 1949(Culbertson, 1949. Culbertson pointed out that Hoyer "reported that the urease activity of Brucella abortus strains is much lower than that of Brucella melitensis or Brucella suis strains, and that the urease test, used quantitatively, represents an additional aid in differentiating Brucella cultures."Our findings were somewhat different from Hoyer's. B. abortus in some experiments seemed to have slightly less urease activity than B. melitensis and B. suis; in most cases, however, it was not possible to observe significant differences between B. melitensis and B. abortus strains. What was striking in our experiments was the greater urease activity of B. suis strains.We used both Ferguson and Hook's (1943) and Christensen's (1946) media, the first as modified by Anderson (1945). The cultures were 24 strains of B. abortus, 9 strains of B. suis, and 6 strains of B. melitensis, of known origin and reidentified previously by routine tests.With Ferguson and Hook's medium in 10-by-80-mm test tubes, in amounts of 0.2 ml, we observed that a loopful from 4-day agar-ascites cultures of all the B. suis strains completely changed the color of the medium to red in 30 seconds or less, even when the loop was still in contact with the medium. The color change only began after 1 to 4 minutes with the B. abortus and B. melitensis strains and was complete after some minutes more.In order to see the intensity of the reaction, we distributed the same medium in amounts of 2 ml in 12-by-120-mm test tubes and inserted between the cotton plug and the glass a strip of filter paper (Chardin) previously soaked in the same phenol red solution used in the medium; these strips hung 5 cm from the mouth of the tube. With the same amount of Brucella cultures, the medium became pink and red after a few minutes with 9 B. suis strains, whereas several minutes and often over an hour were necessary to obtain similar results with 6 B. melitensis and 18 B. abortus strains (6 strains of B. abortus were not used in that experiment). The tubes were watched undisturbed at room temperature; the moment at which the free tip of the strip began to turn pink was timed. This

METABOLIC CHARACTERIZATION OF THE GENUS BRUCELLA I

“…Since there is a loose but none the less apparent host preference exhibited by each of the Brucella species, it is of epidemiological significance to identify correctly these organisms. It is of importance, therefore, that the impasse among investigators concerning the reliability of the determinative methods and the recognition of the species be resolved (Meyer and Eddie, 1930;Huddleson, 1929Huddleson, , 1931Huddleson, , 1957Meyer and ZoBell, 1932;Taylor, Lisbonne, and Roman, 1932;Wilson, 1933;Veazie and Meyer, 1936;Kabler and MacLanahan, 1936;Castenada, Tovar, and Velez, 1942;Brim, Morris, and Sunkes, 1950;Hoyer, 1950;Pacheco and Thiago de Mello, 1950;Renoux and Quatrefages, 1951;McCullough and Beal, 1951;Renoux, 1952;Sanders and Warner, 1953;Pickett, Nelson, and Liberman, 1953;Bruni and de Felip, 1954;Pickett and Nelson, 1955;von Sprockhoff and Strauch, 1955;Spink, 1956;Pital, Cooper, and Leise, 1958;Meyer and Cameron, 1959;Stableforth and Galloway, 1959;Renoux, 1960).…”