L 63
BACTERIOLOGICAL EXAMINATION OF WATER,
Eighty-six samples of water have been examined during the year 1910 compared with 54 in 1909 and 29 in 1908.
Sixty-five (65) of the 86 samples were taken from the Public Water Supplies, i.e., Pokfulam, Tytam and Kowloon supplies; the others were from various sources.
Only the samples from the Public Water Supplies are of any general interest and as the method of taking the samples and of examining them has been altered by me, it is perhaps as well to put the methods used on record here. Without some knowledge of the media and method used, it is impossible to interpret the results properly.
(1.) The samples are taken in each case immediately before and immediately after filtration at the Filter Beds. No samples are taken from the mains or elsewhere and the unfiltered water is always examined at the same time as the filtered.
(2.) Full details as to the rate of filtration, age and composition of Filter Beds, etc., are required.
(3.) The examination is made on an Agar Basis—Gelatine plates are not used.
etc., 1 cc. and 1 cc. of the sample are added to Agar Tubes. (+10 Eyre scale) and plates are poured, incubated at 37°C for 48 hours and counted for total organisms.
T cc., 1 cc. and 2 cc. of the sample are added to MacConkey's Neutral-Red Bile Salt Lactose Agar Tubes and plates are poured, incubated at 37° C. for 48 hours and examined for Coli-like colonies. If any are present, they are picked off on to Agar Slopes and tested for character as given below.
1 cc., 2 cc. and 5 cc. of the sample are added to tubes of MacConkey's Neutral-Red Bile Salt Glucose Peptone Water, incubated at 37° C. for 48 hours and examined for Acid and Gas formation, Dunham's tubes being used.
1 cc., 2 cc., 5 cc., 10 cc., 20 cc. and 50 cc. of the sample are added to MacConkey's Neutral-Red Bile Salt Lactose Peptone Water and examined for Acid and Gas after incubation at 37° C. for 48 hours, Dunham's tubes being used and double strength Peptone Solution being used as required.
The three lowest Lactose tubes showing Acid and Gas are plated out on to a Lactose Agar medium, either MacConkey's Neutral-Red Bile Salt Lactose Agar, Endo's medium, Fawcett's medium or Drigalski-Conradi. The plating is done by sterile glass rods on dried plates.
Page 270
Page 271
L 63
p
BACTERIOLOGICAL EXAMINATION OF WATER,
Eighty-six samples of water have been examined during the year 1910 compared with 54 in 1909 and 29 in 1908.
Sixty-five (65) of the 86 samples were taken from the Public Water Supplies, i.e., Pokfulam, Tytam and Kowloon supplies; the others were from various sources.
Only the samples from the Public Water Supplies are of any general interest and as the method of taking the samples and of examining them has been altered by me, it is perhaps as well to put the methods used on record here. Without some knowledge of the media and method used, it is impossible to interpret the results properly
(1.) The samples are taken in each case immediately before and immediately after filtration at the Filter Beds. No samples are taken from the mains or elesewhere and the unfiltered water is always examined at the same time as the filtered.
(2.) Full details as to the rate of filtration, age and composition of Filter Beds, etc., are required.
(3.) The examination is made on an Agar Basis-Gelatine plates are not used.
Tec., 1 cc. and 1 cc. of the sample are added to Agar Tubes. (+10 Eyre scale) and plates are poured, incubated at 37°C for 48 hours and counted for total organisms.
T cc.,
1 cc. and 2 cc. of the sample are added to MacConkey's Neutral-Red Bile Salt Lactose Agar Tubes and plates are poured, incubated at 37° C. for 48 hours and examined for Coli-like colonies. If any are present, they are picked off on to Agar Slopes and tested for character as given below.
1 cc., 2 cc. and 5 cc. of the sample are added to tubes of MacConkey's Neutral-Red Bile Salt Glucose Peptone Water, incubated at 37° C. for 48 hours and examined for Acid and Gas formation, Dunhan's tubes being used.
1 cc., 2 cc., 5 cc., 10 cc., 20 ec. and 50 cc. of the sample are added to MacConkey's Neutral-Red Bile Salt Lactose Peptone Water and examined for Acid and Gas after incubation at 37° C. for 48 hours, Dunhan's tubes being used and double strength Peptone Solution being used as required.
The three lowest Lactose tubes showing Acid and Gas are plated out on to a Lactose Agar medium, either MacConkey's Neutral-Red Bile Salt Lactose Agar, Endo's medium, Fawcer's medium or Drigalski-Conradi. The plating is done by sterile glass rods on dried plates.
Page 270Page 271
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