366 SOME PROBLEMS IN WATER BACTERIOLOGY 



Indeed, Bardsley' has recently reported imperfect correlation between the Koser and 

 other tests on the basis of results from 1,441 strains. For those bacteriologists who in- 

 sist that "fecal" coli are the only significant type, reasonably accurate results are ob- 

 tainable. 



The present methods recommended^ for completing the coli-aerogenes group test 

 in water analysis consist in transferring material from a positive lactose-broth tube to 

 Endo medium or eosin-methylene-blue agar. Typical colonies are then tested for lac- 

 tose fermentation and are also transferred to nutrient agar slants for morphological 

 study. The completion of the test requires from three to five days. If results are based 

 upon finding so-called "fecal" coli, several more days are consumed. It would be of 

 great advantage to the water-works manager if tests could be devised to give results 

 in twenty-four or forty-eight hours. The use of brilliant green bile in place of lactose 

 broth for the initial tests has already been mentioned. At the present time this is a 

 doubtful procedure. However, recent work has indicated that such a medium may be 

 valuable in shortening the time for the completion of the "coli" test. H. E. Jordan,^ in 

 collaboration with a number of other laboratory workers, has found a 97 per cent cor- 

 relation between the fermentations obtained in a medium containing 2 per cent bile 

 and 1:75,000 brilliant green and the "Standard Methods" completed test, when the 

 brilliant green bile medium is used to confirm originally positive lactose fermentation. 

 Ruchhoft^ has also obtained encouraging results with this method. These original fer- 

 mentations may be due to members of the coli-aerogenes group, to anaerobic organ- 

 isms, or to spore-forming, lactose-fermenting aerobes. The significance of these latter 

 organisms has been studied by Norton and Weight^ and others. What part bacterial 

 "synergism"^ may play in obtaining fermentation in lactose broth in routine water 

 analysis is problematical. The introduction of brilliant green lactose bile as a con- 

 firmatory medium appears to the writer to be a real contribution to sanitary water 

 analysis. 



Attempts to improve upon Endo medium and eosin-methylene-blue agar for isola- 

 tion of Bad. coli do not appear to the writer to represent fruitful research. There ap- 

 pears to be some peculiar fascination to the laboratory worker in devising new com- 

 binations of dyes for differential purposes in all bacteriological work. The most recent 

 attempt to improve upon eosin-methylene-blue has been made by Salle." His medium 

 consists of a mixture of ery throsin, methylene blue, and brom-cresol-purple in a lac- 

 tose-peptone agar buffered with phosphates. 



CLOSTRIDIUM WELCHII 



Since the early work of Klein and Houston,* English bacteriologists have shown 

 interest in the use of Clostridium welchii as an indicator of pollution in water supplies. 

 ' Bardsley, D. A.: J. Hyg., 25, 11. 1926. 



' Standard Methods of Water Analysis (5th ed.). Am. Pub. Health Assoc. 1925. 

 3 Jordan, H. E.: J.A.W.W.A., 18, 337. 1927. 

 " Ruchhoft, C. C: /. A.W.W.A., 16, 778. 1926. 



s Norton, J. F., and Weight, J. J.: Am. J. Pub. Health, 14, 1019. 1924. 

 '' Holraan, W. L., and Meekison, D. M.: /. Infect. Dis., 39, 145. 1926. 

 1 Salle, A. J.: ibid., 41, i. 1927. 

 * Klein, E., and Houston, A. C: Suppl. 2jth Ann. Rep. of Loc. Gov. Bd, 1898. 



