232 PUBLIC HEALTH BACTERIOLOGY 



luxuriant than B. coli ; Gram-negative ; produces acid but 

 no gas in dextrose broth and agar, no change with lactose 

 or saccharose, no clot in milk, but in litmus milk slight acid 

 at first, from small quantity of monosaccharid present ; 

 later, deep blue from formation of alkali ; no indol in 

 peptone water ; on potato slight moist glistening growth, 

 becoming dull and velvety. 



Cultures. In broth : uniform turbidity. In gelatin stab : 

 growth to bottom of stab, and on surface as a thin leaf- 

 like film or pellicle with irregular wavy margin. In gelatin 

 plate, the colonies are smaller, more delicate, and more 

 transparent than those of the colon bacillus of the same 

 age. In agar plates, in twenty-four hours, small greyish 

 colonies are formed, at first transparent but later opaque. 

 On acid potato : slight moist glistening growth. 



Forms acid but no gas with dextrose, laevulose, galactose, 

 maltose, mannite, and dextrin ; but no change with lactose 

 and saccharose. 



In Hiss's tube medium (agar, gelatin, dextrose, Liebig's 

 extract, salt, water), it gives uniform clouding owing to 

 its motility, but no gas ; whereas dysentery bacillus grows 

 only along stab, and colon bacilli form sky-rocket-like 

 figures, and the medium is broken with gas bubbles. 



Optimum temperature, 37 C. ; range 15 to 41 C. 

 Resistance like most non-sporing organisms, 30 min. at 

 6o C., or 2 to 3 min. at ioo C. In ordinary tap or distilled 

 water it is usually found dead in three weeks (Frankland). 

 The researches of Dr. A. C. Houston have shown that in 

 the crude river water derived from the Thames, raw 

 typhoid bacilli die out in one to two weeks, whereas 

 cultivated typhoid bacilli may persist for five weeks. On 

 this basis, the storage of water for thirty days, preliminary 

 to filtration, is looked upon as of prime importance in all 

 waters derived from sources polluted by sewage. 



Does not multiply in water, even when impure. Is by 

 preference a parasite, and when found outside the body 

 can be usually traced to sewage of typhoid patient or 

 convalescent (carrier). In natural bodies of water it 

 retains its vitality for at least four to five days, and in 

 sterile water it may be found surviving for three months. 

 History of typhoid epidemics from sewage-polluted water 



