Question

Your organism is catalase negative and produces a black precipiate on bile. What other test would likely be positive? HTML Editore B I A AI = = = = = = = = = VX Y GD 12pt Paragraph O words uizzes/123342/take ORI PrtScn Home End &

Answer 1

Catalase test is used to identify organisms which produce the enzyme catalase. This enzyme detoxifies hydrogen peroxide by breaking it down into water and oxygen gas. In the e above question the given organism showed negative catalase test which means that the organism can't produce the enzyme catalase. Bile esculin agar is a selective and differential medium which tests the ability of the organism to hydrolyze esculin in the prescene of bile. Esculatin reacts with ferric citrate in the medium to form phenolic iron complex which turns dark brown to black. The organism in the question showed positive bile esculin test with the prescene of black precipitate on bile. The other test which are likely to be shown positive by this organism would be PYR test and Voges Proskauer test. Pyrrolidonyl Arylamidase (PYR) test ia a rapid test which isn used for the presumptive identification of group A beta-hemolytic Streptococci and Enterococci. The positive test is indicated by the development of a deep cherry red colour within a minute of addittion of the reagent. Voges Proskauer or Methyl Red test is used to determine which fermentation pathway is used to utilize glucose. The Voges Proskauer test detects the presence of acetoin, a precursor of 2,3-butanediol. The positive test is indicated by formation of brownish-red to pink colour.