Which test is commonly used to identify Pseudomonas aeruginosa in clinical specimens?

Which test is commonly used to identify Pseudomonas aeruginosa in clinical specimens?

• A. Oxidase test
• B. Catalase test
• C. Coagulase test
• D. Indole test

Answer: (A)

Oxidase activity is used to identify Pseudomonas aeruginosa. This bacterium is oxidase-positive due to the presence of cytochrome c oxidase, so applying the oxidase reagent yields a rapid color change to purple when the enzyme is present. This makes the oxidase test a quick and reliable way to distinguish Pseudomonas from many other Gram‑negative rods, particularly Enterobacterales that are oxidase negative. The other tests don’t provide the same level of diagnostic specificity for Pseudomonas: catalase is common to many aerobes and isn’t distinctive for this organism; coagulase identifies Staphylococcus aureus; indole differentiates certain Enterobacteriaceae based on tryptophanase activity.

Oxidase activity is used to identify Pseudomonas aeruginosa. This bacterium is oxidase-positive due to the presence of cytochrome c oxidase, so applying the oxidase reagent yields a rapid color change to purple when the enzyme is present. This makes the oxidase test a quick and reliable way to distinguish Pseudomonas from many other Gram‑negative rods, particularly Enterobacterales that are oxidase negative. The other tests don’t provide the same level of diagnostic specificity for Pseudomonas: catalase is common to many aerobes and isn’t distinctive for this organism; coagulase identifies Staphylococcus aureus; indole differentiates certain Enterobacteriaceae based on tryptophanase activity.