Which of the following organisms is oxidase-positive?

Moraxella osloensis is recognized as oxidase-positive because it possesses the enzyme cytochrome c oxidase, which is involved in the electron transport chain of aerobic respiration. The presence of this enzyme allows the organism to utilize oxygen and is indicative of its metabolic capabilities. When cultured on an appropriate medium, moraxella species can produce a color change in the presence of an oxidase reagent, confirming its positive status.

In contrast, the other organisms listed generally fall under the oxidase-negative category. Xanthomonas maltophilia and both biotypes of Acinetobacter calcoaceticus (anitratus and iwoffi) do not possess this particular enzyme, meaning they cannot be oxidase-positive. This distinction is important for laboratory identification and helps guide further clinical decisions in diagnosing infections. Identifying oxidase-positive versus oxidase-negative organisms is a fundamental technique in bacteriology that aids in differentiating between species.