The genus Klebsiella belongs to the family Enterobacteriaceae. It consist of Gram-negative straight rods, often surrounded by a capsule. Klebsiella spp. are found in a variety of environmental situations, soil, plants, water, industrial wastewaters, plant products and fresh vegetables. The cells are surrounded by a hydrophilic polysaccharide capsule. The Voges-Proskauer test is positive. Acetoin and 2,3-butanediol are produced during glucose fermentation. Esculin is hydrolyzed. Following compounds are utilized as sole carbon and energy source: L-alanine, L-arabinose, D-arabitol, L-aspartate, D-cellobiose, citrate, D-fructose, L-fucose, fumarate, D-galactose, gentiobiose, D-gluconate, D-glucosamine; D-glucose, DL-glycerate, glycerol....

Gram-negative; rod-shaped; facultatively anaerobic; nonmotile; non-acid-fast; chemoorganoheterotrophic; exhibit a respiratory and fermentative metabolism; catalase-positive; reduce nitrate to nitrite; some strains do not form acetoin and 2,3-butanediol; Voges Proskauer negative; associated with rhinoscleroma (chronic granulomatous disease of the nose).