CHAPTER 19 

 PFEIFFERELLA, AND CERTAIN ALLIED ORGANISMS 



Definition (emended from the American Committee's Report). 



Small, slender, usually non-motile, Gram-negative rods, often staining irregularly 



and sometimes forming threads or showing a tendency towards branching. Growth 



on all media is rather slow ; gelatin may be slowly liquefied ; fermentation of 



carbohydrates is very weak ; characteristic brown honey-Uke growth on potato. 



Type species is Pfeifferella mallei. 



History. — The glanders bacillus was isolated by Loeffler and Schtitz in 1882 

 (see Loeffler 1886) from a horse dying of acute glanders. An organism in many 

 respects resembling Pf. mallei was isolated by Whitmore and Krishnaswami 

 (1912) from a glanders-like disease of human beings in Rangoon. It was desig- 

 nated B. pseudoniallei by Whitmore (1913). Subsequently Stanton and Fletcher 

 (1921, 1925) gave the name of Melioidosis to this disease and Bacillus whitmori 

 to the causative organism. 



The genus Pfeifferella was tentatively created by the American Committee as 

 one of the genera intermediate in position between Actinomyces on the one hand 

 and Mycobacterium on the other. The type species, and the only listed member 

 of the group, is the glanders bacillus or Pf. mallei. The classification of this 

 organism presents many difficulties, and it is by no means certain that the genus 

 Pfeifferella wiU gain permanent recognition. 



As regards the fermentative powers of Pf. mallei, the American Committee's 

 definition states that carbohydrates are not fermented. According to our observa- 

 tions, and those of Stanton and Fletcher (1932), acid is formed in glucose in 2 to 3 

 weeks ; a small amount of acid, sufficient however to give a pink colour with 

 Andrade's indicator, is produced in salicin. Moreover, there is a slow formation 

 of acid in litmus milk, becoming apparent in about 5 days, and followed in 2 to 3 

 weeks by definite clotting. 



In certain respects Whitmore's bacillus resembles Pf. mallei, but it differs 

 from it in many others. For the moment we assign it to the Pfeifferella group, 

 entering a caveat that, should that genus attain a permanent place in systematic 

 bacteriology, it is by no means certain that Whitmore's bacillus will be placed 

 within it. 



Group Characteristics. 



Morphologically the two organisms are fairly similar ; Pf. whitmori, however, 

 is rather smaller, frequently shows bipolar staining, and is motile. In films of the 

 smooth form, the organisms are arranged in long parallel bundles embedded in 

 an interstitial substance, presenting a very characteristic appearance ; with 

 Loeffler's methylene blue, the interstitial substance stains blue, the bacilli bluish- 



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