5G6 PATHOGENIC AEROBIC BACILLI 



Morphology. Bacilli about as long 1 as the tvplioid bacillus, but not so 

 thick, very frequently united in pairs ; occasionally grows out into filaments. 



Biological Characters. An aerobic and facultative anaerobic, lique- 

 fying, non-motile bacillus. Does not form spores. Thermal death point, 60 D 

 C. Stains with the usual aniline colors but not by Gram's method. Grows 

 best at 10 to 15 C. The growth in gelatin is quite characteristic. At the 

 end of two or three days, in gelatin plates, at the room temperature, small 

 white colonies are developed ; in four or five days small gas bubbles or ex- 

 cavations are seen, at the bottom of which lie the scale-like or rosetta-formed 

 colonies. The margin of the colonies is irregular and later jagged. At 

 first the colonies are grayish- white or yellowish, later brownish. The 

 superficial colonies have a peculiar lustre. In gelatin stab cultures, colo- 

 nies develop along the line of puncture, which at first resemble the growtli 

 of Streptococcus pyogenes, and no development is seen on the surface. At 

 the end of five to seven days in place of the line of colonies is seen a channel 

 filled with air, or gas developed by the separate colonies, the bubbles from 

 which coalesce. The funnel formed in this way is somewhat larger above, 

 and at the bottom contains a whitish sediment consisting of bacteria con- 

 tained in a few drops of liquefied gelatin. Along the sides of the funnel 

 bubble-like cavities may frequently be seen, at the bottom of which the bac- 

 teria have accumulated. In bouillon a slight cloudiness is seen near the 

 surface, on the walls of the test tube; when slightly shaken this falls to the 

 bottom, leaving the bouillon entirely clear. In agar -agar tubes, a veil- 

 like stripe develops along the line of puncture, and a grayish-yellow, moist 

 layer, with irregular outlines upon the surface. After some weeks this 

 acquires a brown color. No growth occurs upon potato. No development 

 occurs in the incubating oven at 37" C. 



Pathogenesis. Trout became infected and died through direct infection, 

 subcutaneous or intramuscular inoculations, or through the addition of cul- 

 tures to the water in which they were kept, or by placing infected fish in the 

 same tank with healthy ones. 



BACILLUS OF BECK. 



Synonym. Der Bacillus der Brustseuche beim Kaninchen. 



Obtained by Beck (1892) from rabbits which died of an infectious malady 

 in the Institut fur Infectionskrankheiten, in Berlin, 



Morphology. Very small and slender bacilli, about twice as long and 

 twice as thick as the influenza bacillus ; some what pointed at the extremities ; 

 show a tendency to grow out into filaments. 



Biological Characters. An aerobic (strict) non-liquefying, non-motile 

 bacillus. Spore formation not observed. Grows at the room-temperature 

 and more vigorously at 38 J C. Does not stain by Gram's method. Thermal 

 death point, 50 C. (five minutes). Resists desiccation, at the room tempera- 

 ture, for seventeen days, at 37 C. for three days. 



On gelatin plates, at the end of forty-eight hours, small, finely granular, 

 glass-like colonies are developed ; older colonies have a pale-brown appear- 

 ance. In gelatin stab cultures a granular growth of a white color is seen 

 along the line of puncture. Upon agar, at 37 C., an abundant development 

 occurs in twenty -four hours. The line of puncture seen from above is gray- 

 ish-white, by transmitted light bluish and porcelain-like with a brownish 

 tint. On agar plates the colonies have a yellowish-gray appearance ; the 

 margin of the finely granular colonies is sharply defined. In agar cultures 

 several days old the colonies are sticky and may be picked up as a compact 

 mass, or drawn out into threads. In bouillon, at 37 C., there is a slight 

 cloudiness at the end of twenty-four hours ; later the bouillon is clear and a 

 white sediment is seen at the bottom of the tube. In bouillon cultures 

 especially, the bacillus grows out into long filaments. 



