CHAPTER XXIX 

 BACILLUS PYOCYANEUS 



The bacillus pyocyaneus is primarily a saprophytic organism and occurs in 

 dust, soil and water and substances contaminated by them. 



Morphology. Bacillus pyocyaneus is i to 2 /x long and 0.5 /z wide, sometimes 

 as in old broth cultures elongated forms are observed. It is arranged singly and 

 in short filaments and is actively motile. 



Staining. It stains with all the usual anilin stains and is Gram negative; 

 old cultures (involution forms) may show granular or irregular staining. 



Growth. Bacillus pyocyaneus is an aerobic and facultative anaerobic organ- 

 ism growing at temperatures between i8C. and 43C., best at 37C. Culti- 

 vated under aerobic conditions, it produces pigment-pyocyanine. This pig- 

 ment diffuses through the medium containing the bacilli and gives it a greenish 

 or bluish tint. This pigment can be separated into two or three portions as 

 follows : 



To a bouillon culture showing color add about one-tenth its volume of 

 chloroform, shake, allow to stand at rest until chloroform precipitates. The 

 chloroform is a deep blue and the upper part of the bouillon shows a fluorescent 

 green. 



Bouillon. Incubated at 37C. becomes cloudy in 12 hours; then pigment 

 begins to appear, at first at the surface, later throughout the medium. After 

 several days a thick, whitish pellicle forms on the surface; later an abundant 

 precipitate is thrown down and the medium changes from greenish-blue to 

 yellowish-brown. 



Agar. Growth appears in 24 hours and covers the entire surface in several 

 days and the agar attains a greenish color. 



Gelatin surface cultures after 48 hours at 2oC. to 25C., show small, round 

 yellowish granular colonies; later the dense central portion of the colonies is 

 surrounded by a thin, granular filamentous zone. Liquefaction begins around 

 the colonies and rapidly involves the entire medium. The gelatin is tinted like 

 agar. 



Gelatin. Stab cultures show growth along the stab in 48 hours. The gelatin 

 is tinted green and liquefied. 



Potato. A thick brown surface growth develops in 2 or 3 days. 



MacConkey's bile-salt medium shows gas formation and a decided greenish 

 tint in 24 to 48 hours. 



Bacillus pyocyaneus does not form spores. 



Toxin. Bacillus pyocyaneus forms an intracellular toxin capable of produc- 

 ing effect similar to that caused by the living bacillus. 



Agglutinins are present in the blood of immunized animals. 



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