Fowl Typhoid and Fowl Cholera 
75 
MORPHOLOGICAL STUDIES 
Hie Pasteurella avicida is a nonmotile, gram negative organism showing 
no capsule, endo spores or irregular forms. The size of the organism varies, 
the average being 0.3 by 0.5 microns. The ends are rounded, the organism 
stains bi-polar, which tendency is sometimes lost on prolonged cultivation in 
artificial medium. 
Cultural Characteristics 
Agar Slant (Glycerine). — (Fig. 31.) The growth is scanty; echinulate; 
raised; smooth; glistening, and gives no odor. 
Agar Colonies (Glycerine).—P. avicida makes rapid growth on agar, the 
colonies being punctiform, smooth, raised, entire, and of mucid consistency. 
Gelatin Stab. There is a translucent uniform growth; non-liquifying 
with the medium remaining unchanged. 
Potato. —There is no growth on potato. 
Nutrient Broth.— There is no surface growth; slight turpidity; no odor; 
heavy viscid sediment in 5 days. 
Temperature Relations. —The optimum temperature for growth is 3 7% 
degrees C., with slight tolerance to extremes of heat or cold. 
Reaction to Medium. —Luxuriant growth is obtained on 3 % neutral 
glyceiine agar; P. avicida has little tolerance to organic acids. 
Production of Indole. —Indole is formed with the Salkowsli test; slight 
formation with the vanilin test, and with the Ehrlich test in some in¬ 
stances. These reactions are not consistent. 
Chromogenisis. —The organism is non-chromogenic. 
. Relation to Free Oxygen.—Slight aerobic growth on glucose-agar shake 
in 24 hours. 
Milk. —Milk is unchanged. 
Nitrate Reduction. —Nitrates are reduced. 
Hydrolysis of Starch. Slight diastatic reduction on starch agar. 
