Transmission of haemolytic streptococci

Abstract

1. A study of factors involved in the transmission of haemolytic streptococci has been made by experiments with healthy carriers and individuals whose upper respiratory passages were contaminated withChromobacterium prodigiosum.2. The following conclusions were reached: (a) Expulsion of haemolytic streptococci in droplet spray is determined by the nature of the expiratory activity (Fig. 1), the concentration of the organism in the saliva (Table 3) and the volume of salivary flow (Fig. 6).(b) Droplets and droplet-nuclei are less important vehicles of transmission because of the extremely low content of haemolytic streptococci in them (Figs. 2–5)(c) Dust particles carrying haemolytic streptococci and liberated by agitation of handkerchiefs more effectively pollute the air than violent expiratory activities (Figs. 4 and 5).(d) Hands and clothing readily become contaminated by heavy nasal carriers (Table 4) and the former serve as the principal means of contaminating the environment and other individuals.3. A diagram showing probable mechanisms of transmission is given (Fig. 7) in which hand contact is represented as a more important pathway of spread than air-borne dust which, in turn, is more important than either droplets or droplet-nuclei.