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MANUAL OF DETERMINATIVE BACTERIOLOGY 



Genus I. Rickettsia da Rocha-Lima. 



(Berl. klin. Wchnschr., 53, 1916, 567-569.) Named for Howard Taylor Ricketts 

 who lost his life studying typhus fever. 



Small, often pleomorphic, rod-shaped to coccoid organisms occurring intracyto- 

 plasmically in lice, fleas, ticks and mites, or sometimes intranuclearly. Stain lightly 

 with aniline dyes. Gram-negative. Non-filterable. Have not been cultivated in 

 cell-free media. Parasites of man and animals which are the etiological agents of 

 epidemic typhus, murine or endemic typhus, Rocky Mountain spotted fever, tsu- 

 tsugamushi disease, rickettsialpox and other diseases. 



For reasons that are discussed elsewhere (Bengtson, Jour. Bact., 53, 1947, 325) 

 the genus Dermocentroxenus has been united with the genus Rickettsia. 



The type species is Rickettsia proivazekii da Rocha-Lima.* 



Key to the species of genus Rickettsia. 



I. Louse-borne. 

 II. Flea-borne. 



III. Tick-borne. 



IV. Mite-borne. 



1. Rickettsia prowazekii. 



2. Rickettsia typhi. 



3. Rickettsia rickettsii. 



4. Rickettsia conorii. 



5. Rickettsia tsutsugamushi . 



6. Rickettsia akari. 



1. Rickettsia prowazekii da Rocha- 

 Lima. (da Rocha-Lima, Berl. klin. 

 Wchnschr., 53, 1916, 567; Rickettsia 

 exanthematotyphi Kodama, Kitasato 

 Arch. Exper. Med., 9, 1932, 360; Rickett- 

 sia prowazeki var. prowazeki Pinkerton, 

 Parasitology, 28, 1936, 186; Rickettsia 

 prowazeki sub-species prowazeki Philip, 

 Amer. Jour. Hyg., 37, 1943, 307.) Named 

 for S. von Prowazek who lost his life 

 studying typhus fever. 



Minute coccoid, ellipsoidal and ovoid 

 forms to short rods, sometimes long rods 

 and occasionally filamentous forms, often 

 in pairs and occasionally in chains. In 

 infected lice the minute coccoid and 



paired coccoid forms predominate over 

 the short and long rods and the filamen- 

 tous forms which are up to 40 microns in 

 length. Single elements 0.25 by 0.4 to 

 0.3 by 0.45 micron. Pairs range from 

 0.25 by 0.7 to 0.3 by 1.1 microns. In 

 yolk sacs the organisms vary in size from 

 minute coccoid forms in heavily infected 

 tissue to rod forms resembling small 

 bacteria in lightly infected tissue. 

 Within the same smear of infected mam- 

 malian cells and in chick embryo tissue 

 the organisms are quite uniform in size 

 and morphology. Occur intracytoplas- 

 mically in vascular endothelial cells and 

 in serosal cells. Non-motile. 



* The Editors of the Manual follow Recommendation XL of the International 

 Botanical Code (see p. 59) in regard to the endings used for specific names. This 

 calls for the use of the ii ending for epithets taken from the name of a man ending in 

 a consonant (except names ending in er). Some students of the Rickettsiaceae fol- 

 low the International Rules of Zoological Nomenclature which use ii only in case the 

 name used was employed and declined in Latin. Zoologists use the single i for 

 modern patronymics based on all other names of men. 



