58 BACTERIA IN WATER 



Most bacteriologists would condemn a water containing the 

 typical B. coli in 1 c.c. as showing signs of sewage pollution. In the 

 case of a recent pollution the presence of B. coli affords therefore a 

 much more delicate test of pollution than any chemical examination 

 which can be made.* 



B. enteritidis sporogenes is another organism of indication as to 

 sewage pollution, and its presence in bacillary form or as spores is 

 now accepted as showing recent or remote contamination. 



The presence of streptococcus is held by many bacteriologists to 

 be a sign of sewage contamination, although some contend that the 

 presence of streptococci does not indicate dangerous contamination 

 unless accompanied by B. coli. The following table (p. 59), from the 

 Thirty-fourth Annual Eeport of the Lawrence Sta., 1903, sets forth, 

 in less space and with more accuracy than could be recorded in many 

 words, the relative presence of the chief organisms of contamination, 

 and it is therefore inserted. 



Lastly, there are a number of organisms which appear to be fre- 

 quently present in waters contaminated with sewage, and are rarely 

 if ever found in pure supplies. The occurrence of such bacteria in a 

 water should arouse suspicion as to its origin or contamination. 

 Among this group of bacteria are B. fluorescens putridus, B. erythro- 

 spores, B. et M. urece y B. pyocyaneus, B. lactis cyanogenus, and B. 

 megaterium. 



(3) The presence of pathogenic species. The presence of any 

 pathogenic organisms, in however few numbers, is of course sufficient 

 for the condemnation of a water. For instance, the presence of the 

 bacillus of typhoid fever or the bacillus of cholera at once condemns 

 a water. There are very few authentic records of such organisms 

 being found, and it is therefore necessary to judge of waters by the 

 presence of organisms of contamination. 



Note. A water may be considered safe and potable (a) if it 

 contains comparatively few organisms; (b) an absence of organisms 

 capable of fermenting glucose or lactose media; (c) an absence of 

 B. enteritidis sporogenes; and (d) an absence of any pathogenic 

 species, and especially if these conditions are found to exist as a 

 result of several examinations or of periodic examinations. A water 

 should be condemned, as a rule, (a) if it contains a very large 

 number of bacteria per c.c. of whatever kind; (b) if it contains 

 B. coli communis, or B. enteritidis sporogenes or streptococci in 1 c.c. or 

 any such small quantity; (c) if it gives the enteritidis change in milk 

 cultures , or ferments glucose or lactose media. It should be con- 

 demned without hesitation if it contains B. coli and B. enteritidis sporo- 

 genes (or spores), and streptococci, or if it contains any pathogenic 

 organism, in however small a quantity. But in condemning or 

 * See also Fourth Report Roy. Com. Sewage Disposal, 1904, pp. 106-109. 



