Hippurate hydrolysis test is most helpful in differentiating which group of organisms?

Hippurate hydrolysis test is most helpful in differentiating which group of organisms?

• A. Enterobacteriaceae
• B. Gram-negative cocci
• C. Gram-positive, spore-forming bacilli
• D. Beta-hemolytic Gram-positive cocci

Answer: (D)

Hippurate hydrolysis checks for the enzyme hippuricase, which cleaves hippurate into glycine and benzoic acid. Glycine is detected by a color change after adding a reagent (ninhydrin), so a positive result appears as a blue-violet color. In clinical lab work, this test is most helpful for differentiating Group B Streptococcus—beta-hemolytic, gram-positive cocci—from other beta-hemolytic streptococci, which are usually hippurate-negative. This makes the test a practical tool specifically for distinguishing beta-hemolytic Gram-positive cocci, rather than Gram-negative organisms, Gram-positive spore-formers, or non-hemolytic cocci.

Hippurate hydrolysis checks for the enzyme hippuricase, which cleaves hippurate into glycine and benzoic acid. Glycine is detected by a color change after adding a reagent (ninhydrin), so a positive result appears as a blue-violet color. In clinical lab work, this test is most helpful for differentiating Group B Streptococcus—beta-hemolytic, gram-positive cocci—from other beta-hemolytic streptococci, which are usually hippurate-negative. This makes the test a practical tool specifically for distinguishing beta-hemolytic Gram-positive cocci, rather than Gram-negative organisms, Gram-positive spore-formers, or non-hemolytic cocci.