Klebsiella Pneumoniae - Clinical Significance

Clinical Significance

K. pneumoniae can cause the disease Klebsiella pneumonia. They cause destructive changes to human lungs inflammation and hemorrhage with cell death (necrosis) that sometimes produces a thick, bloody, mucoid sputum (currant jelly sputum). Typically these bacteria gain access after a person aspirates colonizing oropharyngeal microbes into the lower respiratory tract.

As a general rule, Klebsiella infections are mostly seen in people with a weakened immune system. Most often illness affects middle-aged and older men with debilitating diseases. This patient population is believed to have impaired respiratory host defenses, including persons with diabetes, alcoholism, malignancy, liver disease, Chronic obstructive pulmonary diseases (COPD), glucocorticoid therapy, renal failure, and certain occupational exposures (such as paper mill workers). Many of these infections are obtained when a person is in the hospital for some other reason (a nosocomial infection).

The most common infection caused by Klebsiella bacteria outside the hospital is pneumonia, typically in the form of bronchopneumonia and also bronchitis. These patients have an increased tendency to develop lung abscess, cavitation, empyema, and pleural adhesions. It has a high death rate of about 50% even with antimicrobial therapy. The mortality rate can be nearly 100% for persons with alcoholism and bacteremia.

In addition to pneumonia, Klebsiella can also cause infections in the urinary tract, lower biliary tract, and surgical wound sites. The range of clinical diseases includes pneumonia, thrombophlebitis, urinary tract infection (UTI), cholecystitis, diarrhea, upper respiratory tract infection, wound infection, osteomyelitis, meningitis, and bacteremia and septicemia. If a person has an invasive device in their body then contamination of the device becomes a risk; for example respiratory support equipment and urinary catheters put patients at increased risk. Also, the use of antibiotics can be a factor that increases the risk of nosocomial infection with Klebsiella bacteria. Sepsis and septic shock can follow entry of the bacteria into the blood.

Two unusual infections of note are from Klebsiella are rhinoscleroma and ozena. Rhinoscleroma is a chronic inflammatory process involving the nasopharynx. Ozena is a chronic atrophic rhinitis that produces necrosis of nasal mucosa and mucopurulent nasal discharge.

Research conducted at King's College, London has implicated molecular mimicry between HLA-B27 and two Klebsiella surface moleculars as the cause of ankylosing spondylitis.

New antibiotic resistant strains of K. pneumoniae are appearing, and it is increasingly found as a nosocomial infection.

Klebsiella ranks second to E. coli for urinary tract infections in older persons. It is also an opportunistic pathogen for patients with chronic pulmonary disease, enteric pathogenicity, nasal mucosa atrophy, and rhinoscleroma. Feces are the most significant source of patient infection, followed by contact with contaminated instruments.