Abstract
Discussion and Sumary
Although it has been shown recently that the air of hospital wards contains beta hemolytic streptococci of the same serological types as those infecting patients in the same wards 5 , 6 it should be emphasized that the strains reported on here came from air breathed by the city population at large. Though our findings indicate that group A streptococci are relatively rare in normal air sampled at random, it is of great interest that, by the tests applied, they are indistinguishable from similar organisms isolated directly from disease processes. Furthermore, it should be noted that 88% of the strains in this small series were of the human pathogenic group A.
It has been estimated by several investigators 7 , 8 , 9 that group A hemolytic streptococci are present in from 3 to 7% of normal throats. None have reported as high a percentage of group A cultures among the hemolytic streptococci of the throat as was found in this series of air streptococci. It is possible that the percentage of group A cultures of air was augmented by the coughing of individuals with group A infections of the throat.
The presence of group A streptococci does not necessarily indicate that they were suspended in droplets in air, for, as shown by studies of hospital air 5 , 6 and as has been demonstrated experimentally by Wells and in this laboratory, bacteria sprayed in air may float for many hours after all droplets have evaporated. In conclusion we agree with Brown and Allison who, after studying the streptococci in the air of scarlet-fever wards, stated, ". . . . and while contact, direct or indirect, is probably of considerable importance in the transmission of infection the possibility of infection via the air other than that due to droplets cannot be dismissed."
Thanks are due to Dr. Beatrice C. Seegal for her interest and assistance as well as to Dr. Rebecca C. Lancefield for a generous contribution of group serums.
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