CHAPTER 18 



FUSIFORMIS 



Definition. Fusiformis. 



Obligate parasites. Anaerobic or microaerophilic. Cells frequently elongated 

 and fusiform, staining somewhat unevenly. Filaments sometimes formed ; non- 

 branching ; sometimes highly i:)leomorphic. Non-motile. No spores. Reaction 

 to Gram variable, but mainly Gram-negative. Growth in laboratory media feeble. 



A number of organisms, anaerobic or microaeropbilic in their oxygen require- 

 ments, have been isolated by different workers from necrotic lesions in man and 

 animals. The first of these was the so-called B. necrophorus, which was 

 observed by Loeffler (1884) in calf diphtheria. In 1896 Vincent described a fusi- 

 form bacillus, frequently associated with a spirochaete, Trep. vincenti (see Chapter 

 79), in necrotic and ulcerative lesions of the throat and other tissues in 

 human beings. Veillon and Zuber (1898), studying the bacterial flora of appendi- 

 citis and other suppurative lesions, described a number of non-sporing anaerobic 

 bacilli, to which they gave the names of B. ramosus, B. serpens, B. fragilis, B. fur- 

 cosus, and B. fusiformis ; this last organism was apparently identical with the 

 fusiform bacillus described by Vincent. Later work has revealed the frequent 

 presence of organisms of this group in the mouth and on the teeth of man and 

 certain animals (Tunnicliff 1906, Elleimann 1907, Varney 1927, Pratt 1927, Slanetz 

 and Rettger 1933, Bachman and Gregor 1936, Pesch and Schmitz 1936, Spaulding 

 and Rettger 1937, Hine and Berry 1937, Kelly 1944), and in the healthy alimentary 

 canal of man (Eggerth and Gagnon 1933, Weiss and Rettger 1937, Misra 1938, 

 Lewis and Rettger 1940, Dragstedt, Dack and Kirsner 1941). With the more 

 general use of improved anaerobic methods they have been found in association 

 with various human infections, especially in France and the United States (see 

 Chapter 79). 



Relatively little attention has been paid to the systematic study of these 

 organisms, and their classification presents considerable difficulties. Castellani 

 and Chalmers (1920) proposed a genus Bacteroides to contain obligatory anaerobic 

 bacilli that did not form spores, and the genus has since been adopted in Bergey's 

 manual, where it covers a variety of morphologically different organisms. The 

 American Committee of Bacteriologists (see Report 1920) have described a genus 

 Fusiformis, for the inclusion of organisms with certain characteristics resembling in 

 some respects those possessed by the Corynebacterium and the Pfeifferella groups. 

 As the definition of this genus (see above) seems to cover the main characteristics 

 of the organisms we have mentioned, it seems permissible, at least for the moment, 

 to include these organisms within it. 



Group Characteristics. — The organisms of this group are typically rod-shaped ; 

 but their size is subject to considerable variation. They may be very short, or they 



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