Klebsiella pneumoniae is a type of Gram-negative, non-motile bacterium that is rod-shaped and made of either one or two pods, with a polysaccharide capsule that envelops the entire cell structure, according to Medscape. This capsule, which accounts for the organism’s large appearance under a microscope, provides robust protection against host defense systems, such as the human immune system.
Klebsiella pneumoniae is the somewhat rare, pulmonary variant of the Klebsiella bacterium, which is much more typically found in the digestive system and in human stool, according to the Centers for Disease Control and Prevention. However, because the bacteria spreads via person-to-person contact, it can and does infect such systems as the pulmonary tract, particularly in health care settings. The bacteria do not spread through the air, according to the CDC. However, they do spread via contaminated hands or through such health care equipment as ventilators or intravenous catheters.
Patients with wounds from injuries or surgeries are also particularly vulnerable to Klebsiella infection. Patients who are taking certain antibiotics over a long term suffer the greatest risk of Klebsiella infection. People suffering from compromised immune systems, such as AIDS and cancer patients, also face a heightened risk of pneumonia when infected with Klebsiella pneumoniae, according to the Pathogen Profile Dictionary.
Certain types of Klebsiella, including Klebsiella pneumoniae, have developed a strong resistance to antibiotics, according to the CDC. The bacteria can produce an enzyme called carbapenemase, which provides the organisms with immunity against a class of antibiotics called carbapenems. Whereas most Klebsiella infections can be treated with conventional antibiotics, these carbapenemase-producing strains require laboratory testing to determine a specific combination of antibiotics that effectively counters the infection.