Germicidal Action of Daylight on Meningococci in the Dried State.

The study reported in the preceding communication (1943) showed that meningococci are much more resistant to dehydration than is generally supposed and that in films dried on glass, wood, or cotton fabric, they can survive for a week or more in the dark. The question of their susceptibility to the germicidal action of direct and diffuse sunlight seemed also to invitereexamination. The observations bearing on this question are few and contradictory and obviously were made in passing by workers concerned primarily with other aspects of the biology of the meningococcus. Of the investigators who dried meningococci in films on glass or other objects, Bettencourt and Franca (1904) and von Lingelsheim (1905) reported them to die as quickly in the dark as in diffuse daylight. The time required for this to occur was 3 to 6 hours according to Bettencourt and Franca who worked in Lisbcn and less than 12 hours in von Lingelsheim's experiments which were made in Upper Silesia. On the other hand, Fliugge (1905) reported some observations made in his laboratory in Breslau by Kache in which dried meningococci died in 10 hours in diffuse daylight and 24 hours in the dark. Additional evidence that diffuse daylight is injurious to meningococci has been contributed by experiments of a different sort. Several workers have noted that stock cultures live longer in the dark than in diffuse daylight at the same temperature, which has usually been room temperature. For example: Elser and Huntoon (1909) found that strains which lived 3 or 4 weeks at room temperature in the dark died within one week when exposed to diffuse daylight. On the deleterious effect of direct sunlight there was agreement among all workers who investigated that point, although they did differ on the rapidity of its lethal action. It is interesting to compare the results reported from different places even though the experiments themselves were not identical. Bettencourt and Franca (1904) working in Lisbon found that exposure to direct sunlight for 2 hours was sufficient to kill meningococci although they were protected against overheating by running water. The date of his experiments was not given. In experiments made by Lingelsheim (1905) in Upper Silesia in June, 4 to 6 hours of direct sunlight was lethal. Kutcher (1906) found 8 to 10 hours of direct sunlight necessary to kill meningococci in March in Berlin. Elser and Huntoon (1909) reported 8 to 9 hours in August in New York City.