Enterobacter aerogenes is usually positive for Voges-Proskauer (VP) and citrate utilization and negative for indole and methyl red.
VP is used to detect acetoin in a bacterial broth culture by adding alpha-naphthol and potassium hydroxide.
Citrate utilization test distinguish between members of the Enterobacteriaceae family based on their metabolic products.
Indole test is used for the determination of the ability of an organism to split tryptophan amino-acid.
Methyl Red (MR) test determines whether the bacteria performs mixed acids fermentation when supplied glucose.