Suggested Grouping of Slow Lactose Fermenting Coliform Organisms

TL;DR: In a recent survey of 25 water laboratories McCrady found that 3 expressed doubt of the sanitary significance of coliforms producing less than 10 per cent gas in presumptive tests, and suggested that " until sufficient evidence to the contrary is pre-

Abstract: DELAYED or weak fermentation of lactose by coliform organisms has been recognized since 1893,1 yet the sanitary significance of such organisms in water and in milk and other foods is still extremely puzzling. In fact, it must be admitted that sanitary quality is not always easily determined even when typical coliform organisms are involved. In a recent survey of 25 water laboratories McCrady 2 found that 3 expressed doubt of the sanitary significance of coliforms producing less than 10 per cent gas in presumptive tests. Two of these laboratories did so on the ground that these organisms were usually found in waters where the sanitary survey indicated an excellent supply. One laboratory doubted their significance because they were considered to be attenuated or devitalized coliform organisms and therefore of little sanitary significance. On the other hand, some of the 15 laboratories attaching full significance to these organisms did so on the ground that they represented attenuated cultures that might be easily rejuvenated under natural conditions. McCrady suggested that " until sufficient evidence to the contrary is pre-