126 ANTISEPTICS 



to tyrocidine. " To tlie first list can be added a Gram- 

 positive yeast which was killed by a fairly large dose 

 of gramicidine and to the second a Gram-negative spore- 

 former which was not affected by the drug. 



These convincing results have been in general con- 

 firmed by those of Downs (1942). There were, however, 

 two exceptions : the meningococcus, which was more sen- 

 sitive to gramicidine than the staphylococcus, and a sen- 

 sitive avirulent strain of Pasteurella tularensis. These 

 exceptions limit the validity of the general conclusion 

 stated above, and, if confirmed, would disprove the con- 

 ception that susceptibility to gramicidine and the prop- 

 erty of Gram staining are due to the same mechanism, or 

 involve the same cell constituents. 



For penicillin, the same selectivity is sometimes claim- 

 ed, but the order of sensitivity as given by Abraham et al. 

 (1941) disproves this contention. Complete inhibition 

 is not accomplished by 1,000 ppm. penicillin with Vibrio 

 cholerae, Salmonella paratyphi and typJiy murium, Kleb- 

 siella pneumoniae, Escherichia coli, Mycobacterium tu- 

 berculosis, Pseudomonas aeruginosa and Brucella meli- 

 tensis. A somewhat higher sensitivity is observed with 

 Pasteurella pestis, Brucella abortus, Shigella dysenteriae; 

 250 ppm. inhibit Streptococcus viridans, Proteus vul- 

 garis, and an anaerobic streptococcus; 100 ppm. suffice 

 for Diplococcus pneumoniae, and Eberthella typhi, 50 

 ppm. for Salmonella enteritidis. Then comes quite a gap 

 in the degree of sensitivity; the next group includes 

 C orynebacterium diphtheriae, inhibited by 8 ppm, and 

 Clostridiwm oedematiens by 3 ppm., while 1 ppm. inhib- 

 its Streptococcus pyogenes. Staphylococcus aureus. Ba- 

 cillus anthracis and Actinomyces bovis. Still more sen- 

 sitive are Clostridium Welchii, inhibited by 0.7 ppm., 

 and Neisseria gonorrhoeae by 0.5 ppm. 



Since, in this list, most of the first-named organisms 

 are Gram-positive and most of the last-named are Gram- 

 negative, there appears to be a parallelism between 



