Which of the following organisms is a common oxidase-positive bacterium?

Campylobacter jejuni is primarily known as a common oxidase-positive bacterium. The oxidase test is used to determine the presence of cytochrome c oxidase in bacteria, which is a component of the electron transport chain. This organism, which is often associated with gastrointestinal infections, exemplifies a group of bacteria that can produce the enzyme needed for oxidase activity, thus giving a positive result in this test.

In laboratory practice, the identification of Campylobacter jejuni is crucial due to its clinical significance in foodborne illnesses, particularly from undercooked poultry, where it is often found. The positive oxidase reaction is an important characteristic that helps differentiate it from other species that may be present in a sample.

Other organisms listed in the choices do not share this oxidase-positive trait. For example, Shigella is known for being oxidase-negative, and it is also a significant pathogen responsible for bacillary dysentery. Haemophilus species can vary in their oxidase activity but are generally not classified as commonly oxidase-positive. Klebsiella pneumoniae, another organism in the list, is typically oxidase-negative and is known for causing various infections, including pneumonia and urinary tract infections. Understanding these distinctions is essential