Klebsiella pneumoniae is a
Gram-negative, non-
motile,
encapsulated,
lactose fermenting,
facultative anaerobic, rod shaped
bacterium found in the normal flora of the mouth, skin, and intestines.
It is clinically the most important member of the
Klebsiella genus of
Enterobacteriaceae; it is closely related to
K. oxytoca from which it is distinguished by being indole-negative and by its ability to grow on both
melezitose and
3-hydroxybutyrate. It naturally occurs in the soil and about 30% of strains can
fix nitrogen in anaerobic condition.
As a free-living
diazotroph, its nitrogen fixation system has been much studied.
Members of the
Klebsiella genus typically express 2 types of antigens on their cell surface. The first, O antigen, is a lipopolysaccharide of which 9 varieties exist. The second is K antigen, a capsular polysaccharide with more than 80 varieties. Both contribute to pathogenicity and form the basis for subtyping.
History
The Danish scientist
Hans Christian Gram (1853–1938), developed the technique now known as
Gram staining in 1884 to discriminate between
K. pneumoniae and
Streptococcus pneumoniae.
Klebsiella was named after the German bacteriologist
Edwin Klebs (1834–1913).
Multiply-resistant
Klebsiella pneumoniae have been killed
in vivo via intraperitoneal, intravenous or intranasal administration of
phages in laboratory tests.
Clinical significance
It can cause
Klebsiella pneumonia.
Research conducted at King's College, London has implicated molecular mimicry between HLA-B27 and two molecules in
Klebsiella microbes as the cause of
ankylosing spondylitis.
As a general rule,
Klebsiella infections tend to occur in people with a weakened immune system from improper diet (alcoholics and diabetics). 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.
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.
See also
