Enterobacter aerogenes is a Gram-negative, oxidase negative, catalase positive, citrate positive, indole negative, rod-shaped bacterium. E. aerogenes is a nosocomial and pathogenic bacterium that causes opportunistic infections including most types of infections.ome of the infections caused by E. aerogenes result from specific antibiotic treatments, venous catheter insertions, and/or surgical procedures. E. aerogenes is generally found in the human gastrointestinal tract and does not generally cause disease in healthy individuals.