THE PRESENCE, TYPE, AND POSSIBLE SIGNIFICANCE OF LACTOSE-FERMENTING BACILLI 325 



Experiment III. was carried out to determine the types of lactose fermenters present 

 in a shallow well situated in a native hoosh, and represented the type common in 

 Khartoum. The degree of pollution present was considerable. The types of lactose 

 fermenters present were, out of ten test colonies: — B. lactis serogenes = 3, B. coacowha = 1, 

 B. neapolitanus = 1, B. coli mutahiiis [Massini) = 1, and four others not identified. 



Additional Expeeiments. (Vide Tables, page 327J 



A. Lactase fermenters in human fseces 



Experiments V. and VI. were carried out for the purpose of ascertaining the types of 

 lactose fermenters present in human ftBces. Experiment V. was carried out in the month 

 of August. Experiment VI. three months later. One gramme of feeces was taken and added 

 to a tube of MacConkey's broth, and the latter well shaken up so as to get as good an 

 emulsion as possible. The tube was incubated then for 24 hours at 37' C. and five loopfuls 

 were removed and inoculated into a tube of sterile water, from which subcultures were 

 made on lactose bile-salt-neutral-red-agar plates. The latter were incubated at 37° C. for 

 48 hours, and, as usual, ten colonies picked off and their reactions tested. 



Eeference to the tables will show that these two experiments illustrate the fact that Seasonal 

 different types of lactose fermenters are apparently present in human faeces in different ™"^''°" °f 

 months of the year and, if this is true, in order to get the fact more fully established, such fermenters in 

 experiments will require to be carried out throughout the year. human feces 



B. Effect of sunlight on lactose fennejiters in hwman faeces 



It is a well-recognised fact that sunlight has a powerful effect on different 

 micro-organisms, and there can be no doubt that the sun's rays in the Tropics play an 

 important part as a bactericidal agent. 



Some rough experiments were carried out to illustrate this, and more especially with 

 reference to the B. coli. Laboratory cultures were not employed, as, apart from the fact 

 that they did not represent the condition of things in nature, Clemesha in India obtained 

 irregular results by using them. 



The procedure adopted was as follows : — 



One gramme of human fseces was made into an emulsion with one litre of sterile water 

 and well mixed. Five c.c. of this mixture was removed and inoculated into MacConkey's 

 bile-salt broth in order to determine the types of lactose fermenters present, and the 

 remainder was put into a glass jar covered with a glass lid, and exposed to the sun's rays. Effect of 

 Samples of 5 c.c. were removed at intervals and plated out to determine the types of sunlight 

 organisms present. Before removing these samples, the jar was well shaken. The 

 temperature of this emulsion varied from 26° C. to 41° C. The depth of the emulsion was 

 not kept constant. The results of this experiment were as follows : — 

 Before exposure 



Organisms present in emulsion. In ten lactose fermenters B. coli= 1, B . neapolitanus = -i, 

 B. vesicnlosiis = 1, and four organisms not identified. 

 After exposure to simlight for 24 hours 



B. coli = nil, B. neapolitanus = 6, B. schxfferi = 1, and three organisms not identified. 

 After exposure to sunlight for 48 hours 



B. coscoroba = 2, and seven others of the B. neapolitanus type. 

 After exposure to sunlight for 6 days 



Organisms belonging to Groups I. and IV. were present. 

 After exposure to sunlight for 10 daijs 



B. schiefferi = 4, B. neapolitanus = 6 



