A microbiologist observes a Gram-negative rod that produces a blue-green pigment on nutrient agar and gives a positive oxidase test. Which of the following organisms is most likely being identified?

Explanation

Pseudomonas aeruginosa is a Gram-negative rod known for its characteristic production of pyocyanin (a blue-green pigment) and its positive oxidase test result. In contrast, Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis are all Gram-negative rods but are typically oxidase-negative and do not produce blue-green pigments.