14. SHELLFISH CONTAMINATION FROM SEWAGE-POLLUTED WATERS. 
Morphology and staining properties.—Gram-negative, more or less 
actively motile bacilli, rods usually straight with slightly rounded 
ends, varying in size from about 0.4 to 0.8 by 1.5 to 4 microns, gener- 
ally somewhat longer and more slender than Bacillus coli. No 
chains, spores, or capsules observed. - 
Biological characters.—Plain agar: Soft, grayish white, moderately 
abundant growth. 
Bile salt agar: Small reddish, slowly developing colonies. 
Peptonized beef broth: Rendered uniformly turbid with no ring 
or membrane. 
Potato: No visible growth. 
Alkaline litmus milk: Unchanged or faintly alkalinized after a 
slight initial acidity. 
Sugar solutions: No gas production in dextrose, lactose, saccharose, 
levulose, maltose, nutrose, and inulin. 
Nitrate solution: Nitrates absent in three-cases, heavy trace in 
fourth. : 
Dunham’s solution: Indol absent or present in slight trace. 
Gelatin: Not liquefied, more or less circular flat, whitish growth 
on surface, filiform stab. 
Agelutination: Negative in two cases with 1:50 dilutions after one 
hour, control stock culture agglutinated with 1:300 dilution of typhoid 
immune serum after fifteen minutes. Owing to difficulty in securing 
serum, the first two cultures were not tested. The typhoid serum 
was furnished by the Hygienic Laboratory of the Public Health and 
Marine-Hospital Service. 
These cultures can not be classified as true types of Bacillus 
typhosus, although biologically they closely resemble this general 
eroup of organisms. 
GENERAL CHARACTERISTICS OF THE BACILLUS COLI ORGANISMS ISOLATED. 
Morphology and staining properties.—-Gram-negative, feebly or 
actively motile, rods generally short and ovoid with rounded ends; 
size varying from 0.4 to 0.9 by 1 to 2.5 microns, with filaments occa- 
sionally much longer. No spores, chains, or capsules observed. 
Biological characters.—Plain agar: Abundant, soft, whitish-gray 
erowth. 
Bile salt agar: Plates usually show moderate-sized, circular, yel- 
lowish-pink colonies. 
Peptonized beef broth: Densely turbid, usually a slight membrane 
with ring and heavy sediment. 
Potato: Brownish, abundant patch, darkening with age. 
Alkaline itmus saville Coagulated generally after two days at 37° C. 
Rosalic aeid solution: Umeheneed. 
le - 
