NOTES ON BACT. COLI AND BACT. AEROGENES 



MAX LEVINE, 



From the Department of Pathology and Bacteriology, 

 State University of Iowa, '' < 



Iowa City, Iowa. 



Read before Laboratory Section, American Public Health Association, at San Francisco, Cal., 



September 16, 1920. 



Accurate information on the relative incidence of Bact. coli 

 and Bact. aerogenes in nature would aid materially in the inter- 

 pretation of the colon test in water analysis. Professor Levine 

 suggests the lines along which selective media, for the isolation 

 of these organisms, may be devised. 



IN studies on the distribution of B. 

 coli and B. aerogenes, the author has 

 given preference to the plate method 

 of isolation. This, also, seems to be the 

 view of most other investigators who 

 have concerned themselves with similar 

 studies. In water analysis, on the other 

 hand, the plate method of direct isolation 

 is inconvenient and practically impos- 

 sible when dealing with large samples 

 (10 to 100 cc.), and preliminary enrich- 

 ment, therefore, is resorted to. What 

 happens in the preliminary enrichment 

 tube as to the relative abundance of B. 

 coli and B. aerogenes, is not definitely 

 known as far as the author is aware. 

 Overgrowths of one or the other of these 

 organisms in the preliminary enrichment 

 tube make it extremely difficult, if not 

 impossible, to correlate the water results 

 with the findings that have been reported 

 (with the plate method) on the distribu- 

 tion of B. coli and B. aerogenes in nature. 

 The author has felt for some time that 

 before much light will be thrown on the 

 true relative incidence of B. coli and B. 

 aerogenes in water and in feces, etc., it 

 will be necessary first, so to modify our 

 preliminary enrichment media, or other 

 conditions, as to enable the investigator 

 to isolate or suppress either B. coli or 

 B. aerogenes at will. 



With this in mind, studies were begun 

 to determine the influence of various 



factors such as dyes, bile-salts, concen- 

 tration of peptone, etc., on the rate of 

 multiplication of B. coli. In general, it 

 was found 



(1) That B. coli would not grow in 

 y 2 percent peptone with crystal violent 

 in a dilution of 1-200,000, or brilliant 

 green in a dilution of 1-1,000,000. 



(2) That bile-salts stimulated the 

 growth of B. coli when the concentration 

 was less than 0.5 percent, but showed a 

 marked inhibitory action if the concen- 

 tration were raised to 0.7 or 1.0 percent. 

 It was intended to continue this work 

 with B. aerogenes, but the outbreak of 

 the war interfered with the plans. The 

 following factors are now being studied 

 as to their influence on the growth of 

 B. coli and B. aerogenes. 



1 . Temperature. 



2. Boric acid. 



3. Crystal violet. 



4. Brilliant green. 

 Temperature. That B. coli and B. 



aerogenes have different optimum growth 

 temperatures may be inferred from the 

 literature. Rogers and his associates 

 have often mentioned the necessity for 

 using a relatively low temperature (30 

 C.) for growth of some strains of B. 

 aerogenes isolated from grains. Sim- 

 ilarly Rettger reports that in studying 

 the distribution of the colon group in un- 

 polluted soils a temperature of 30 C. 



Reprinted from January, 1921, issue of the American Journal of Public Health. 



