106 APPLIED BACTERIOLOGY FOR NURSES 



when treated according to Gram's method. They 

 grow readily on various media, but prefer media con- 

 taining blood or blood-serum. Many varieties of 

 streptococci have a peculiar dissolving effect on blood, 

 so that, when grown on solid media containing blood, 

 each colony is seen to be surrounded by a clear zone. 

 We speak of such varieties as "hemolyzing" (blood- 

 dissolving) streptococci. 



Streptococcus pyogenes is the cause of a great variety 

 of infections in man. Among these may be mentioned 

 erysipelas, cellulitis, sepsis, puerperal infection, acute 

 peritonitis, tonsillitis, bronchopneumonia, otitis media, 

 and its complicating mastoiditis, meningitis, enteritis, 

 endocarditis, synovitis, and arthritis. It must not be 

 understood, however, that these infections are always 

 due to streptococcus pyogenes, for we have already 

 learned that other bacteria may be the cause. A number 

 of observers hold that scarlet fever is a streptococcus 

 infection, but the general opinion is that this organism 

 is merely a secondary invader, probably through the 

 tonsils. 



The Streptococcus pyogenes, fortunately, is not dif- 

 ficult to kill. Thus, an exposure to a temperature 

 of 130 F. for from ten to twenty* minutes ordinarily 

 suffices. Bichlorid of mercury, 1:5000, carbolic acid, 

 1 per cent., lysol, J per cent., kill the germ in a few 

 minutes. 



It should be unnecessary to enumerate all the pre- 

 cautions which a nurse should take in preventing the 

 spread of streptococcus infection to others. They 

 will differ, of course, with the kind of infection one is 

 dealing with. It is well to remember, however, that 



