Which genus is most associated with identification by the porphyrin test?

• A. Campylobacter
• B. Haemophilus
• C. Moraxella
• D. Neisseria

Answer: (B)

Porphyrin testing looks at whether a bacterium can manufacture porphyrins, compounds in the heme biosynthesis pathway. Haemophilus species are classically tied to this test because some members can synthesize porphyrins on their own, so they yield a positive porphyrin test. This property helps distinguish Haemophilus from other genera in routine lab work. For example, within Haemophilus, porphyrin production can separate certain species from others, and it’s a traditional tool used when identifying this genus. In practice, the other genera listed aren’t characterized by this test in routine identification, so Haemophilus is the genus most associated with the porphyrin test.