AXTISEPTICS ] 23 



II. SELECTIVE ACTION OF ANTISEPTICS 



At the beginning- of the discussion of chemical dis- 

 infection, it was pointed out that the strong disinfectants 

 kill different species of bacteria at nearly the same rate, 

 while dyes, benzoic and salicylic acid, and a number of 

 therapeutic agents show marked differences in their ef- 

 fects upon different groups of bacteria. Most of the se- 

 lective compounds must be considered as antiseptics 

 rather than as disinfectants. Selectivity indicates that 

 the cell mechanism upon which these substances act dif- 

 fers in those species which show different resistance. 



The most commonly claimed instance of selectivity is 

 that between Gram-positive and Gram-negative bacteria. 

 Such correlation between staining property and vital 

 function would be a very great help to the biochemist. 

 However, a closer analysis shows that many such claims 

 are generalizations from tests with only very few species, 

 and are by no means based upon a representative selec- 

 tion of Gram-positive and Gram-negative genera. If 

 the tests are made only with Staphylococcus aureus and 

 Bacterium typliosum, the two officially designated test 

 species for disinfectants, no conclusion can be derived 

 for other Gram-positive or Gram-negative organisms. 

 If Hartmann (1936) had not included two bacilli in his 

 study of the action of sodium azide (Table 23) he might 

 have generalized and concluded that Gram-positive bac- 

 teria are more resistant than Gram-negative. The re- 

 sults obtained with the two bacilli proved conclusively 

 that there was no correlation between Gram staining and 

 azide sensitivity. We shall, however, present here the 

 evidence from the literature for and against the corre- 

 lation. 



Diernhofer (1936), in an attempt to find a medium in 

 which the mastitis streptococcus would outgrow the co- 



