What characteristic differentiates Aeromonas spp. on selective enteric media?

Aeromonas species are differentiated on selective enteric media primarily by their oxidase positive reaction. This characteristic is essential in distinguishing them from other genera commonly found in the same environments, such as Enterobacteriaceae, which are oxidase negative. The presence of the oxidase enzyme allows Aeromonas spp. to produce a blue color when treated with oxidase reagent, indicating their unique metabolic capability.

While Aeromonas spp. are indeed Gram negative, this characteristic is not exclusive to them, as many other bacteria also share this feature. Urease production may vary among different species, making it not a definitive characteristic for identification. Indole production can also occur in various bacteria, but it is not a primary means of identification for Aeromonas spp. Therefore, oxidase positivity stands out as a key differentiating factor on selective enteric media.