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, nut rose, and iriulin. 



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. 



Agglutination : 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 

 group of organisms. 



GENERAL CHARACTERISTICS OF THE BACILLUS COLI ORGANISMS ISOLATED. 



MorpJiology 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 jobserved. 



Biological characters. Plain agar: Abundant, soft, whitish-gray 

 growth. 



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 litmus milk: Coagulated generally after two days at 37 C. 



Rosalie acid solution: Unchanged. 



