'S'26 TH1-; I'UKSKNCE, TYI'K, ANM) I'OSSlllLK SIUNII-'ICANCK OF LACTOSE-FERMENTINi; liU 11,1,1 



EHect of soil 



Lactose 

 fermenters in 

 Goat's fneces 



After crfiiisnir in nunh'ght for 30 dai/a 



H. rosrorohii = 2, li. schiefferi = 4, H. iieapdlilaniis = 3, B. veniculosiit = 1. 



The results of these experiments tend to show that li. coli communis is extremely 

 susceptible to the bactericidal efifects of sunlight, and that B. coscoroba, B. schmffvrl, 

 B. neapolitaniif and B. venctilosux are extremely resistant. The average period of 

 sunshine per diem during these experiments was 11^ hours. 



Experiments were also carried out for th(; purpose of ascertaining the bactericidal 



effects of the sun on all fji-cal organisms. Small quantities of tlu; emulsion, /.c 1 c.c, were 



removed at intervals and plated out on lactose bile-salt-neutral-red-agar and incubated 



for -18 hours at 27° C. 



Before exposure to sualij;lit = colouics too uumerous to count 

 After 1 hour = colonies too numerous to count 



„ 6 hours = between 800 and 900 



„ -24 hours = lietwueu -200 and 300 



A large number of experiments must still be carried out before it will be possible 

 to classify the organisms in this country according to the effects of sunlight on them. 

 But this will be possible if work be conducted on the lines suggested by Clemesha, and 

 the results of such research will aid considerably in adopting a bacteriological standard 

 for drinking-water from surface sources. 



G. Effect of earth burial on the bacterial content of human excrement 



One other important factor in nature, closely associated with the bacteriology of 

 water, has also to be considered, and that is the effect of soil on the bacteria in human 

 excrement and the way in whicli nature gets rid of soil pollution of this kind. In order 

 to study such effects, samples were taken from the trenching grounds where all the 

 sewage of the town is pitted. The soil is of a loamy nature and the excreta are buried in 

 pits 18 to 24 inches deep. Samples were removed from a depth of 4 inches, and one gramme 

 placed in MacConkey's bile-salt broth and incubated for 24 hours at 37° C. Subcultures 

 wore taken and plated out on lactose bile-salt-neutral-red-agar and various colonies 

 picked off and put into the different media. 



The experiments showed that B. coli, though present in 24 hours, was not found in 

 the contents of trenches 7 days old, and that such sun-resisting oi-ganisms as B. schsefferi, 

 B. neapolitanus and B. vesiculosus were still present in trenches 14 days old. 

 D. Lactose fermenters in animal excreta 



In this country the part played by animal pollution of water-supplies cannot be 

 overlooked. The commonest animal owned by the native in the Sudan is the goat. The 

 types of organisms met with in the fajces of the goat were B. coli, B. cloacne, B. neapolitanus 

 and others which have not been identified. 



In the faeces of the cow B. neapolitanus and B. schiefferi were present, and there were 

 several that gave a positive Voges-Proskauer reaction. According to MacConkey, these 

 latter organisms are closelj' associated with the B. lactis leroijenes and B. cloacx group. 



No conclusions as regards the effect of sunlight and soil on the facal organisms of 

 these animals have yet been arrived at as further experiments are in process of being 

 carried out. 



The lack of completeness in these experiments prevents any definite conclusions being 

 stated as regards the adoption of a bacteriological standard for drinking-water derived 

 from surface sources in this country. As mentioned above, they only represent a 

 preliminary introduction to an extensive research that is being carried out on a subject 

 of great importance. 



