The Genus Klebsiella
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The Genus Klebsiella SYLVAIN BRISSE, FRANCINE GRIMONT AND PATRICK A. D. GRIMONT
Taxonomic History and Structure Historical Developments The genus Klebsiella, in the family Enterobacteriaceae, was named by Trevisan (1885) to honor the German microbiologist Edwin Klebs (1834– 1913). The type species is Klebsiella pneumoniae (Schroeter, 1886; Trevisan, 1887). The first Klebsiella species ever described was a capsulated bacillus from patients with rhinoscleroma (Von Frisch, 1882). The organism was named “Klebsiella rhinoscleromatis” by Trevisan (1887). Abel (1893) observed a capsulated bacillus, “Bacillus mucosus ozaenae” from the nasal secretion of patients with ozaena. The bacterium was later transferred to the genus Klebsiella as K. ozaenae (Bergey et al., 1925). Friedländer (1982) described a bacterium from the lungs of a patient who had died of pneumonia. The organism was named “Hyalococcus pneumoniae “ (Schroeter, 1889) and Klebsiella pneumoniae (Trevisan, 1887). Considerable confusion occurred for many years since the organism could not be objectively separated from the bacterium Escherich described as “Bacterium lactis aerogenes” (Escherich, 1885) and which was renamed “Bacillus aerogenes” (Kruse, 1896), “Aerobacter aerogenes” (Kruse, 1896), and later Enterobacter aerogenes (Hormaeche and Edwards, 1960). Both K. pneumoniae and “Aerobacter aerogenes” fermented many carbohydrates (often with gas production), gave a positive Voges-Proskauer reaction and reacted with Klebsiella capsular antisera. A step forward was taken when Møller (1955) introduced the decarboxylase tests. Klebsiella pneumoniae was defined as nonmotile and ornithine decarboxylase negative, whereas “A. aerogenes” was defined as motile or nonmotile and ornithine decarboxylase positive (Hormaeche and Edwards, 1958). To reduce confusion in communication, a new genus Enterobacter was formed (Hormaeche and Edwards, 1960) in which “A. aerogenes” was transferred as E. aerogenes. Historically, this separation was probably arbitrary (authentic strains being unavailable), but these
redescriptions and the designation of neotype strains solved the problem for most microbiologists. However, E. aerogenes is much closer to Klebsiella species than to Enterobacter cloacae on the basis of phenotypic traits and DNA relatedness (Bascomb et al., 1971; Brenner et al., 1972; Steigerwalt et al., 1976; Izard et al., 1980) and 16S rRNA sequence (Boye and Hansen, 2003). The transfer of E. aerogenes to the genus Klebsiella as K. mobilis has been proposed (Bascomb et al., 1971). Nomenclatural confusion remained for some time in the United Kingdom where a biogroup of K. pneumoniae was named “Klebsiella aerogenes” (Taylor et al., 1956). Cowan et al. (1960) subdivided K. pneumoniae sensu lato into K. pneumoniae (sensu stricto), “K. aerogenes,” “K. edwardsii subsp. Edwardsii,” and “K. edwardsii subsp. Atlantae.” Authentic or typical strains of K. pneumoniae, “K. edwardsii” and “K. aerogenes” cannot be differentiated by DNA relatedness or p
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