Pneumonia (Klebsiella pneumoniae)
Friedlander pneumonia usually causes consolidation in more than one lobe. Histologically, it is characterized by necrosis and often leads to lung abscess. This organism is often the cause of chronic infection in cases of bronchiectasis, but in cystic fibrosis the causative organism is more likely to be Pseudomonas aeruginosa.
The genus Klebsiella belongs to the tribe Klebsiellae, a member of the family Enterobacteriaceae. Named after Edwin Klebs, a 19th century German microbiologist, Klebsiellae are nonmotile, rod-shaped, gram-negative bacteria. They bear a prominent polysaccharide capsule which encases the entire cell surface. Resistance against many host defense mechanisms is provided by the capsule. K. pneumoniae is an opportunistic organism present in the environment and on the mucosa. Pneumonia secondary to this organism is also known as Friedlander’s pneumonia. Infection in the lungs of debilitated patients, especially alcoholics, results in necrosis, inflammation, and hemorrhage. A thick, tenacious, gelatinous sputum described as “currant jelly” is produced. Pulmonary involvement is usually in the form of bronchopneumonia or bronchitis. Infection can be community-acquired or nosocomial.