Which organism is associated with a blue-green pigment and is oxidase positive, commonly linked to burn wound infections?

• A. Chromobacterium violaceum
• B. Legionella pneumophila
• C. Pseudomonas aeruginosa
• D. Serratia marcescens

Answer: (C)

Pseudomonas aeruginosa is known for producing a blue-green pigment called pyocyanin, often accompanied by another pigment (pyoverdin) that can give colonies a yellow-green fluorescence. This distinctive coloration, along with being oxidase positive (meaning it has cytochrome c oxidase in its respiratory chain), is a classic clue for identifying this organism in the lab. In burn patients, the skin barrier is compromised and the wound environment becomes moist and nutrient-rich, which Pseudomonas thrives in, making it a common cause of burn wound infections. The oxidase-positive result helps separate nonfermenting Gram-negative rods like Pseudomonas from many other Gram-negative bacteria that are oxidase negative.

For context, Chromobacterium violaceum can produce a purple pigment and is also oxidase positive, but it is not the organism most typically associated with burn wound infections. Legionella pneumophila is a different pathogen with a tendency toward pneumonia; Serratia marcescens produces a red pigment (prodiginos) and is generally oxidase negative, so it does not match the blue-green pigment and oxidase-positive profile described.