Chryseobacterium spp. are distinguished from Acinetobacter spp. by which two tests?

Chryseobacterium spp. are differentiated from Acinetobacter spp. primarily through their oxidase test and their growth characteristics on MacConkey agar. Chryseobacterium spp. are generally oxidase positive, which means that they can produce the enzyme cytochrome c oxidase, resulting in a color change when a specific reagent is added. In contrast, Acinetobacter spp. are usually oxidase negative.

Furthermore, when cultured on MacConkey agar, Chryseobacterium spp. can ferment lactose leading to the formation of pink colonies, while Acinetobacter typically does not demonstrate significant lactose fermentation, resulting in colony appearance that does not change the medium color. This ability to grow on MacConkey agar and the distinct results of the oxidase test are critical for microbiologists when identifying and distinguishing between these two genera in clinical or environmental samples.