Klebsiella pneumoniae [Theodore A.E. Klebs; Gk, pneumon, lung] , a species of gram-negative, nonmotile bacteria found in soil, water, cereal grains, and the intestinal tract of humans and other animals. It is associated with several pathological conditions, including pneumonia. It is commonly implicated in nosocomial urinary tract infections, especially in immunocompromised patients. Also called Friedländer’s bacillus.