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''Klebsiella pneumoniae'' is a Gram-negative, nonmotile, encapsulated, lactose-fermenting, facultative anaerobic, rod-shaped bacterium. Although found in the normal flora of the mouth, skin, and intestines, it can cause destructive changes to human and animal lungs if aspirated (inhaled), specifically to the alveoli (in the lungs) resulting in bloody sputum. In the clinical setting, it is the most significant member of the ''Klebsiella'' genus of Enterobacteriaceae. ''K oxytoca'' and ''K rhinoscleromatis'' have also been demonstrated in human clinical specimens. In recent years, klebsiellae have become important pathogens in nosocomial infections. It naturally occurs in the soil, and about 30% of strains can fix nitrogen in anaerobic conditions. As a free-living diazotroph, its nitrogen fixation system has been much-studied, and is of agricultural interest, as ''K. pneumoniae'' has been demonstrated to increase crop yields in agricultural conditions. Members of the ''Klebsiella'' genus typically express two types of antigens on their cell surfaces. The first, O antigen, is a component of the lipopolysaccharide (LPS), 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 serogrouping. It is closely related to ''K. oxytoca'' from which it is distinguished by being indole-negative and by its ability to grow on melezitose but not 3-hydroxybutyrate. == History == 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''. The genus ''Klebsiella'' was named after the German bacteriologist Edwin Klebs (1834–1913). Also known as Friedlander's Bacillum in honor of Carl Friedlander, a German pathologist, who proposed that this bacterium was the etiological factor for the pneumonia seen specially in immunocompromised individuals such as sufferers of chronic diseases or alcoholics. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Klebsiella pneumoniae」の詳細全文を読む スポンサード リンク
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