BACILLUS PYOCYANEUS 127 



Resistance. -Bacillus pyocyaneus is somewhat more resistant to heat and 

 chemical germicides than the typhoid bacillus. Soil seems to be its normal 

 abode and it survives in water longer than either the typhoid or colon bacillus. 



Pathogenesis. Bacillus pyocyaneus, present in eggs, milk, ice cream and 

 other articles of food, for a long time before consumption, can produce changes 

 which result in acute gastroenteritis or toxemia when such food is eaten. 



It may produce gastro-enteritis especially in debilitated children. 



Bacillus pyocyaneus is frequently present upon the skin and occasionally in 

 the mouth or nose of healthy people without causing ill effect. Healthy indi- 

 viduals seem to be immune to this organism. But when injury or infection 

 with some other organism reduces the vitality to a marked degree, then bacillus 

 pyocyaneus may enter the devitalized part and further aggravate the condition. 

 Thus, it is most commonly found in chronic suppurative conditions, in advanced 

 phthisis and extensive, grossly infected wounds. 



Diagnosis. Pus containing bacillus pyocyaneus usually has a distinct green- 

 ish color which suggests its presence. If the pus is smeared on a slide, fixed by 

 heat and stained by Gram's method and a short, slim, Gram negative bacillus 

 found it is sufficient to indicate the presence of bacillus pyocyaneus. 



More exact identification may be obtained by inoculating bouillon, agar or 

 gelatin and observing the pigment formation. It should be remembered in this 

 connection that cultures direct from tissue or pus sometimes do not show pig- 

 ment production until subcultured once or twice; that pigment appears only 

 under aerobic conditions. 



