Paper I
Question
List four oxidase positive organisms
Answer
Four oxidase-positive organisms (possessing cytochrome c oxidase, detected by the oxidase test — an important test distinguishing certain clinically important Gram-negative organisms from the oxidase-negative Enterobacteriaceae):
- Pseudomonas aeruginosa.
- Neisseria gonorrhoeae (and N. meningitidis).
- Vibrio cholerae.
- Campylobacter jejuni.
(Other valid examples: Haemophilus influenzae, Aeromonas species, Pasteurella multocida, Legionella pneumophila.)
Clinical relevance: the oxidase test is a key first-step differentiating test in routine bacterial identification — a negative result is characteristic of (and helps identify) all members of the family Enterobacteriaceae (e.g., E. coli, Salmonella, Shigella, Klebsiella), which are uniformly oxidase-negative.