How can Enterobacter sakazakii be differentiated from Enterobacter cloacae?

Enterobacter sakazakii can be differentiated from Enterobacter cloacae through specific biochemical tests that reveal distinct characteristics of each species. The correct choice involves yellow pigmentation and the inability to ferment sorbitol, which is a notable trait of Enterobacter sakazakii. This bacterium typically exhibits yellow pigmentation on culture media, which can be attributed to the production of certain pigments during growth.

In addition, Enterobacter sakazakii is characterized by its negative sorbitol fermentation, meaning it does not metabolize sorbitol to produce acid, while Enterobacter cloacae can ferment sorbitol. This combination of yellow pigmentation and negative sorbitol fermentation serves as a reliable identification method, allowing microbiologists to distinguish between these two closely related species.

The other options do not provide the correct characteristics for differentiating the two species. For instance, pink pigmentation and positive arginine dihydrolase are characteristics associated with other Enterobacter species but not specific enough to distinguish Enterobacter sakazakii from Enterobacter cloacae. Similarly, yellow pigmentation and positive urease or H2S production on TSI do not serve as effective differentiation methods between these two particular Enterobacter spp.