668 



Bacillus Icteroides 



high as I 1250 and consider reaction in a dilution of less than i 1300 without 

 diagnostic value. 



Bacillus Icteroides (Sanarelli) 



General Characteristics. — An actively motile flagellated, non-sporogenous 

 non-liquefying, non-chromogenic, aerogenic, aerobic and optionally anaerobic, 

 pathogenic bacillus which stains by the ordinary method, but not by Gram's 

 method. It produces indol, but does not coagulate milk. 

 Sanarelli* regarded this bacillus as the specific organism of yellow fever. He 

 found it in 11 autopsies upon yellow fever cases, but al- 

 ways in association with streptococci, colon bacilli, pro- 

 teus, and other organisms. It is found in the blood 

 and tissues, and not in the gastro-intestinal tract, and 

 isolation of the organism was possible in only 58 per cent, 

 of the cases, and only in rare instances was accomplished 

 during life. 



Distribution.^ — By suitable methods it can be foutid in 

 the organs of yellow fever cadavers, usually aggregated 

 in small groups, in the capillaries of the liver, kidneys, 

 and other organs. The best method of demonstration is 

 to keep a fragment of liver, obtained from a body soon 

 after death, in the incubator at 37°C. for twelve hours, 

 and allow the bacteria to multiply in the tissue before ex- 

 amination. 



Morphology. — The bacillus presents nothing morpho- 

 logically characteristic. It is a small pleomorphous . 

 bacillus with rounded ends, usually joined in pairs. It is 

 2, to 4 M in length, and, as a rule, two or three times 

 longer than broad. It is actively motile and has flageUa. 

 It does not form spores. 



Staining. — It stains by the usual methods, but not by 

 Gram's method. 



Cultivation. — The bacillus can be grown upon the usual 

 media. It grows readily at ordinary room temperatures, 

 but best at 37°C. 



Colonies. — Upon gelatin plates it forms rounded, trans- 

 parent, granular colonies, which during the first three or 

 four days somewhat resemble leukocytes. The granular 

 appearance becomes continuously more marked, and usu- 

 ally an opaque central or peripheral nucleus is seen. In 

 time the entire colony becomes opaque, but does not 

 liquefy gelatin. 



Gelalm. — Stroke cultures on obliquely solidified gelatin 

 show brilliant, opaque, white colonies resembling drops of 

 milk. The medium is not liquefied. 



Bouillon. — In bouillon it develops slowly, without either 

 pellicle or flocculi. 



Agar-agar.^ — The culture upon agar-agar is said to be 

 characteristic. 



The peculiar and characteristic appearances of the 

 colonies do not develop if grown at 37°C.; but at 20° to 

 2 2°C. the colonies appear rounded, whitish, opaque, and 

 prominent, like drops of milk. This appearance of the 

 colonies also shows well if the cultures are kept for the first twelve to sixteen 

 hours at 37°C., and afterward at the room temperature, when the colonies will 

 show a flat central nucleus transparent and bluish, surrounded by a prominent 

 and opaque zone, the whole resembling a drop of sealing-wax. Sanarelli refers to 

 this appearance as constituting the chief diagnostic feature of Bacillus icteroi- 

 des. It can be observed in twenty-four hours. 

 Blood-serum.— Upon blood-serum the growth is very meager. 

 Potato. — The growth upon potato corresponds with that of the bacillus of 

 typhoid fever. 



* II Policlinico, 1897, iv, Nos. 8-9, p. i. 



Fig. 263. — Cul- 

 ture of Bacillus 

 icteroides on 

 (Sanarelli). 



agar 



