Klebsiella pneumoniae is a Gram-negative, nonmotile, encapsulated, lactose-fermenting, facultative anaerobic, rod-shaped bacterium. It can cause destructive changes to human lungs. It naturally occurs in the soil, and can fix nitrogen in anaerobic conditions. In the clinical setting, it is the most significant member of the Klebsiella genus of
Enterobacteriaceae. In recent years, klebsiellae have become important pathogens in nosocomial infections. Klebsiella pneumoniae liver abscess (KLA) is an emerging infectious liver disease in developed countries such as the United States.