48 



BACTERIA IN WATER 



nitroso-indol) does not appear at once, the culture may be incubated for a brief 

 period. 



Reduction of nitrate. B. coli is a vigorous denitrifying organism. In twenty- 

 four hours at 37 C. the reduction of nitrates to nitrites is well marked. (Bouillon 

 5 per cent., KNO 3 0*1 per cent., water 94*9 per cent.). 



Aerobic or facultative anaerobic. 



Vitality and powers of resistance, not considerable, but more than the typhoid 

 bacillus. 



The following table of comparative features of B. coli and B. typhoons is a 

 provisional scheme of some of the differences between a typical B. coli and a 

 typical typhoid bacillus. As is pointed out elsewhere, the Coli group is large and 

 its characteristics vary according to origin, race, cultivation, and many other 

 conditions. In some ways the table is misleading, as it is exceptional to find a 

 bacillus which gives all these features, but the table is inserted for reference, 

 because in a general way it states the broad differences between the types : 



Comparative Features 



B. typhosus. 

 Morphology Bacillus of unequal lengths; 



some filaments. 

 Flagella Long, wavy, spiral, numerous 



(9 to 18) ; movement very active. 



On gelatine and agar Angular, irregular, 



slightly raised colonies ; slow growth ; 



medium remains clear. 

 In gelatine In ordinary gelatine and in 



lactose gelatine no gas is produced (at 



20 CA No liquefaction. 

 Milk Not curdled by the bacillus (at 



37 C.). No acid production. 

 Indol In bouillon and Witte's peptone 



water, no production of indol. 

 Bouillon containing 0'3 per cent. Phenol, 



or Formalin (1 : 7000) No growth. 

 Lactose bouillon at 37 C. No gas pro- 

 duction. 



Neutral-red glucose-agar No change. 

 Glucose or lactose media, shake cultures 



No gas production. 

 Potato An "invisible growth" if the 



potato is acid in reaction. 

 25 per cent, gelatine at 37 0. Strongly 



and uniformly turbid (Klein). No 



pellicle. 

 Eisner's iodised potato-gelatine Slow 



growth ; small transparent colonies. 

 Proskauer and Capaldis Medium, No. 1 



No growth ; no change in reaction. 

 Widal's reaction Bacilli became motion- 

 less and agglutinated when suspended 



in blood serum from a typhoid patient. 



(See Appendix.) 

 M'Conkey's lactose agar Surface colonies 



transparent ; medium clear. 

 Vitality in icater or sewage B. typhosus 



soon ceases to multiply and more or 



less readily dies. 

 Pfeiffer's inoculation test with anti-typhoid 



serum Negative result. 



of B. coli and B. typhosus 



B. coli. 



Bacillus shorter and thicker; filaments 

 rare. 



Shorter, stiffer, few (average 3), move- 

 ment less active, and sometimes almost 

 absent. 



Colonies with even margin, homogenous, 

 much larger and quicker growth, 

 medium becomes turbid or coloured. 



Under the same circumstances abundant 

 gas is produced. No liquefaction. 



Milk is curdled, within 24 to 48 hours at 



37 C. Abundant acid production. 

 Indol is present as a rule. 



Grows well and uniformly throughout 



medium. 

 Gas production occurs. 



Marked green fluorescence. 

 Marked gas production. 



Thick, yellowish-white growth, later be- 

 coming brown in colour. 



Gelatine remains clear within 48 hours, 

 but a thick pellicle forms on the 

 surface. 



Rapid growth ; large brown colonies. 



Growth ; acid reaction. 



B. coli remains motile and not aggluti- 

 nated. 



Surface colonies white with yellow 



centre ; haze on medium. 

 B. coli retains vitality and power of 



self-multiplication . 



Positive result, variable symptoms ac- 

 cording to virulence of bacillus. 



