THE INCIDENCE OF BACTERIUM COLI IN FARM WATER SUPPLIES

SUMMARY: Farm water supplies giving 37° positives in MacConkey's broth within 24 hr. had a much higher incidence of presumptive Bact. coli type I than those which gave 37° positives during the second day of incubation only; presumptive Bact. coli reactions were obtained with 85% of the 7,522 tubes positive in 24 hr. compared with 23% for the 7,593 tubes showing positive reactions during the second day at 37°.     

COLI-AEROGENES BACTERIA IN FARM WATER SUPPLIES

SUMMARY: A series of 825 cultures of coli-aerogenes bacteria isolated at 30° and a series of 735 cultures isolated at 37° from 645 samples of farm water supplies were classified according to the recommendations of the Coliform Sub-Committee of the Society for Applied Bacteriology (Report, 1949). Klebsiella constituted 50% of the cultures isolated at 30°, whereas Escherichia coli I was the dominant type, forming 57%, among the cultures isolated at 37°. It would thus appear that isolation at 30° is as selective for Klebsiella as isolation at 37° is for Escherichia . Coli-aerogenes organisms, mainly 37° negative strains of Citrobacter freundii I and K. cloacae , were found in waters of high sanitary quality derived from protected springs and wells; but the coli-aerogenes microflora of polluted water was dominated by E. coli I, which formed 43% of the isolates at 30° and 76% of those at 37°. The results for a series of fortnightly samples from 11 farm water supplies showed a marked seasonal variation in the incidence of different types isolated at 30°; E. coli I formed a higher proportion in summer than in winter, while 37° negative strains of Klebsiella and Citrobacter formed a higher proportion in winter than in summer.     

A NOTE ON THE THERMODURIC BACTERIAL CONTENT OF FARM WATER SUPPLIES

SUMMARY: Significantly higher thermoduric colony counts were obtained when 5 ml. of water were laboratory pasteurized in 5 ml. of sterile milk or 2 ml. of water were pasteurized in 8 ml. of sterile milk, than when 10 ml. of water were directly pasteurized; 86% of the water samples had higher thermoduric counts after pasteurization in milk. Large differences were not common, only 19% of the ratios being over 5 and 5% over 10. Aerobic sporing rods were dominant in the thermoduric microflora irrespective of the method of pasteurization.