Expulsion of group a hemolytic streptococci in droplets and droplet nuclei by sneezing, coughing and talking

Abstract

1. 1. The numbers of beta and alpha streptococci discharged into the air of an experimental room-during sneezing, coughing and talking were determined in a series of forty-eight carriers of group A streptococci. By simultaneous employment of exposed blood agar plates placed upon the floor, and “broth bubbler” samplers whose intake was 3 feet from the floor, streptococci expelled in large, rapidly falling droplets could be differentiated from those discharged as droplet nuclei which remained in the air for at least several minutes. 2. 2. The material dispersed into the air during a sneeze is chiefly saliva. 3. 3. Four dispersion patterns of beta hemolytic streptococci by sneezing were evident. In the most common, moderate numbers were expelled in large droplets which fell rapidly to the floor 1.5 feet from the sneezer, but very few or none in droplet nuclei. In one of two less common patterns, small numbers of beta streptococci were sneezed as droplet nuclei but none in large droplets; in the other, no beta streptococci were recovered from the air. In the rarest, of which only one example was found, large numbers of beta (and alpha) streptococci were expelled both as droplet nuclei and in large droplets; many were collected as far as 9.5 feet from the sneezer. The saliva of this carrier contained huge numbers of beta streptococci. 4. 4. Thirty-five per cent of twenty carriers sneezed out large numbers of alpha (salivary) streptococci as droplet nuclei. Eighty per cent discharged moderate or large numbers in heavy droplets which fell rapidly to the floor. 5. 5. About one-half the streptococci expelled into the air as droplet nuclei by sneezing were still present as long as twenty minutes after the first sneeze. 6. 6. The material expelled during coughing apparently originates in the back of the throat or below the epiglottis and contains little if any saliva. 7. 7. Only one of twenty carriers coughed large numbers of beta streptococci into the air as droplet nuclei or in large droplets; he expelled no alpha streptococci. Ninety-five per cent of the carriers coughed few or no streptococci collected by either type of air culture. 8. 8. Practically no streptococci were recovered from the air of rooms while carriers counted out loud for five minutes.