Bacillus Icteroides, Sanarelli (1897). 



Origin. — In the blood and organs in yellow fever. Although 

 present in small numbers and isolated only in 7 out of 13 cases, it is 

 regarded by Sanarelli as the cause of the disease. 



Form. — Small, very slender rods; two to three times as long as 

 wide. It is usually single or in pairs; short threads are occasionally 

 found in bouillon. In the body and on agar it is almost coccus-like in 

 appearance, whereas in bouillon large rods are met with. Bright 

 polar bodies. 



MoTit-iTY. — Extremely motile, especially in the water of conden- 

 sation on agar. It bears 4-8 long whip's. Splendid giant-whips (Novy). 



Sporulatioi^.— Not observed in cultures of the typical bacillus. 



Anilin dyes.— Stain readily. Gram's method is not applicable. 

 At times, a bi-polar stain may be obtained. 



Growth. — Is rapid and on some media very characteristic. In 

 general, it resembles quite closely that of the typhoid bacillus. 

 Rapidity of growth is like that of B. typhosus and less than that of 

 the colon bacillus. No growth on distinctly acid media. 



Plates. — The colonies on gelatin plates are extremely characteristic. To obtain typi- 

 cal colonies it is necessary to maintain a constant temperature of. 16-18' (See Fig. 33, 

 p. 179); moreover, the gelatin should not be too hard v 10 per cent, or less) and should oe 

 alkalin (ep. 157). Under proper conditions, as indicated, characteristic colonies can be 

 obtained n"om cultures which haveoeen kept in the laboratory for several years (Novy j. 

 Otherwise, atypical colonies will result. 



The deeii colonies are perfectly circular and sharp bordered. .\t first they are light 

 yellow, almost homogeneous, wax-like in appearance. Later they become dark or perfectly 

 black. They may show at the center slight, irregular radiating lines. Atypical colonies are 

 those which do not become black; those which are lobular or are surrounded bj; a fringe of 

 fibrils. The latter two forms are rather rare. The former develop on acid gelatin. 



The surface colony appears to the eye like a droplet of boiled starch or mucus. It is 

 thick and convex. It" may be perfectly circular, but frequently will show a distinct 

 kidney-shape. An opaque, yellowish white 'nucleus can, as a rule, be seen at or near the 

 center; or, in the case of the kidney-shaped colony at the hilum. Under the microscope the 

 border appears colorless, or with a central, light-brown tinge. It is finely granular and the 

 border is sharp perfectly smooth. The nucleus is opaque and may be round, but more 

 often is hat-shaped, and has even been compared to Saturn with its rings. In the kidney- 

 shaped colony the crown of the hat projects into, or is turned toward the hilum. On hard or 

 acid gelatin only atypical colonies form. These are small, raised points usually without the 

 nucleus, and the kidney shape is absent. 



Isolated colonies on inclined agar (p. 239) , developed at 39°, are thin, flat, grayish and 

 circular. If at the end of 24 hours the tubes are placed at 16°, growth at the edge of each 

 colony will continue, but it will take on a thick, slimy character. In two or three days the 

 colonies present a peculiar appearance — a thick, opalescent, slimy ring surrounds a flat, 

 thin, transparent area. When several colonies are close together the slimy growths may 

 coalesce and give rise to rivulets. Eventually, the outer slimy border becomes transparent, 

 and the original colony is seen as an opaque body imbedded in it. 



Stab culture.— \\. grows slowly along the line of inoculation and, unless kept at about 

 25°, does not tend to spread on the surface. ' 



Streak culture. — At 39" on agar, like the B. typhosus it forms a thin, transparent 

 growth. At 16 it forms a thick, moist slimy growth, which is homogeneous and mucous- 

 like in appearance, and is not unlike that of Friedlander's bacillus. On potato, it yields a 

 moist, colorless, invisible growth. On blood-serum a scarcely visible, transparent film forms. 



Bouillon.— ^0 ring or pellicle as a rule, forms on the surface. The liquid is clouded 

 and remains so for some time. Very little sediment in the tube. Involution forms. 



Milk.— Is, not coagulated. Indol reaction is not given, or but very faintly. 



On glucose media it produces gas, also an acid reaction. No growth in Uschinskv's 

 or in Eisner's medium. On Stoddart's medium it forms a thin, transparent, rapidly spread- 

 ing film. Similar diffusion in Hiss's tube medium. 



Oxygen requirements. — It is a facultative anaerobe. 



Temperature. — Has a marked effect upon the character of the 

 growth. Grows at 14-40°. The optimum is at about 37°. 



Behavior to gelatin. —It does not liquefy. 



Attenuation. — It is not affected by freezing for some days. 



Immunity. — An antitoxic serum has not been obtained. Normal 

 blood agglutinates. 



Pathogenesis, Diagnosis. — See p. 382. 



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