Structure and Physiology
Klebsiella pneumoniae is a Gram-negative, rod-shaped, facultative anaerobic bacterium. It is encapsulated and undergoes lactose fermentation for metabolic purposes when conditions allow. This nonmotile bacterium is found in humans within the normal flora of the mouth, skin, and intestines. It is a naturally occurring bacterium in the soil and some strains have the ability to fix nitrogen in anaerobic conditions.