Medical and sanitary report / Government of the Gold Coast.

  • Gold Coast. Medical Department.
Date:
[1918]
Catalogue details

Licence: Public Domain Mark

Credit: Medical and sanitary report / Government of the Gold Coast. Source: Wellcome Collection.

    58/68 (page 54)
    The preliminary trials proving satisfactory, an experiment was tried with excess lime on the ordinary working scale with a view to determining the rate of neutralisation of the excess alkali in such conditions. Low Level Reservoir No. 1 was filled with river water and excess lime added, an excess of 6 parts per 100,000 being aimed at. The filling of the reservoir was completed on the 6th May and the water was found to be free from alkali on the, 10th June. Samples received on the 15th May showed no b. coli in 50cc., the largest amount tested. B. coli was found in 50cc. of a sample taken from this reservoir on the 18th June. It was not, however, present in 50cc. of the same water after passing the filters. The water from Low Level Reservoir No. 1 having become exhausted in August, this reservoir was again used for test purposes. It was filled with limed water between the 9th and 16th September, the amount of excess lime aimed at in this case being 4 parts per 100,000. Neutralisation point was reached on the 1st October. Samples of water from the reservoir and of the same water after passing the filters received on the 1st November contained no b. coli in 50cc., the largest amount tested. Some tests were made with alum, which showed, as was expected, that it had but little power in reducing b. coli. Water direct from the River Densu was examined on the 20th November. B. coli was found in '000 100. At the request of the Senior Sanitary Officer, weekly examinations were made of samples of water taken from various standpipes in Accra and of samples of water after it had passed the filters at Weschiang. In taking the samples from the standpipes no precautions were taken beforehand, such as running the water to waste for some minutes or flaming the tap, as it was desired to procure a sample such as the average individual obtains from these pipes. It was found that while no b. coli was found in 50cc., the largest quantity tested, of the water obtained from the final filters, it was distributed in a capricious way in the water obtained from the standpipes. Houston’s modified ‘ Flaginac ’ method was employed in testing for b. coli. Five different quantities of wafer, 'Glee., 'lee., lcc., lOcc. and 50cc. were added to tubes of MacOonkey’s neutral red bile salt glucose peptone water “ Rebipegluqua.” These tubes were incubated for 48 hours and occasionally for longer periods. From the tube showing acid and gas formation to which the smallest quantity of sample had been added cultures were planted on MacConkey’s neutral red bile salt lactose agar “ Rebipelagar ” and incubated for 24 hours. Subcultures from red colonies on the “ Rebi.pelagar ” were made in lactose peptone water, in saccharose peptone water and in ordinary peptone water. These were incubated for 24-48 hours, when the peptone water was tested for indol and hanging drops examined for motility. The laboratory being without adonite and inulin and only receiving a supply of dulcite towards the end of November, it was not possible to make any attempt at differentiating the organisms found. Of 65 cultures which produced acid and gas in “ Rebipegluqua ” and colonies on “Rebipelagar”, 7 fermented neither lactose nor saccharose, 35 fermented both, 9 fermented lactose alone and 14 saccharose alone. 5 showed no motility and 24 did not seem to produce indol. The number of fermenters of both lactose and saccharose is interesting in view of Houston’s remarks. “ The typical b. coli of the human intestinal tract may be divided into two classes according to their action on saccharose. The majority do not ferment this sugar or act on it only to a slight extent. Hence typical b. coli which do not ferment saccharose would seem to be more significant of undesirable pollution than those which do ferment it.” The high percentage of cultures in which indol was not found is probably due to the facts that the incubation of the peptone water tube was not sufficiently prolonged, and the test used was Salkowski’s without heating. One chemical analysis of water was made at the laboratory during the year and a bacteriological analysis of samples of water was done on three occasions, necessitating the making of 807 cultures.