220 



NATURE OF ANTIBIOTIC ACTION 



gram-positive and the second active against members of both groups. 

 These four compounds show various other differences in the nature of 

 their antibacterial action. Differences in the bactericidal properties of 

 other antibiotic substances are brought out in Table 36. 



Various attempts have been made to compare the antibacterial action 

 of antibiotic substances with that of organic antiseptics. According to 

 Suter (890), the bactericidal action of a compound depends upon cer- 

 tain physical and chemical characters} a property that determines the 

 bactericidal action of the compound upon E. ty-phosa may be relatively 

 unimportant in the case of another organism such as S. aureus. A sub- 

 stance may have the same activity, as expressed by the phenol coeffi- 

 cient, against two organisms and still differ markedly in its relative 



TABLE 35. BACTERIOSTATIC SPECTRA OF FOUR ANTIBIOTIC SUBSTANCES 



GRAM 



TEST ORGANISM STAIN 



S. aureus + 



S. aureus + 



S. lutea + 



B. subtilis 4- 



B. megatherium + 



B. mycoides + 



CI. welchii + 



Actinomyces sp. + 



Neisseria sp. - 



Br. abortus - 



Sh. gallinarum — 



Pasteurella sp. — 



Hemofhilus sp. - 



S. schottmiilleri — 



S. aertrycke - 



Ps. -fiuorescens — 



5. marcescens — 



A . aero genes — 

 E. coli 



E. coli - 



PENI- 

 CILLIN 



9,500* 



I jOOof 



38,000* 



19,000* 



1,900* 



5* 

 i,50ot 

 i,ooot 



2,000t 



it 



<lt 

 10* 



<5* 

 <i* 

 <5* 

 <it 



<5* 



ACTINO- 

 MYCIN 



20,000 



60,000 



60,000 



40,000 



40,000 



1,000 



10 



20 



10 



20 



<I0 



50 



<I0 



10 



<5 

 <5 



STREPTO- 

 THRICIN 



100 

 750 

 200 



<3 



10-50 



100 

 300 

 100 

 30 

 200 



<3 



5 

 30 



CLAVACIN 

 100 



500 



200 

 100 

 200 



60 



6 

 60 

 50 



100 



Note. Activity is indicated in thousands of dilution units per gram. 



• Data based on a sample having 470 Oxford units. 



t Data reported by Abraham et al. (5), based on a less active preparation. 



