286 DISEASE CONTROL 



cocci, and pneumococci is inhibited or the organisms are killed. When 

 applied locally, tyrothricin does not reach the blood stream. It has also 

 been found that tyrothricin has an excellent therapeutic effect when 

 used for urethral irrigations in the male ( 198). In a recent summary, it 

 was reported (528) that tyrothricin can be used successfully as a wet 

 dressing in surgical infections j it was most effective in hemolytic strep- 

 tococcal lesions and next in S. aureus and S. alhus lesions. It actually 

 encouraged the growth of Ps. aeruginosa and C difhtheriae. 



Tyrothricin possesses several limitations, from the point of view of 

 practical utilization: (a) development of bacterial, notably staphylococ- 

 cus, variants, which become resistant to this agent j (b) inhibition of its 

 action by phospholipinsj (c) hemolytic action, which prevents its intra- 

 venous use. 



The filtrate of B. mesentericus was found (984) to have a specific bac- 

 tericidal action on C. difhtheriae in a dilution of 1:1,250. When in- 

 jected parenterally into guinea pigs, it inhibited the toxic effect of the 

 diphtheria organism. The filtrate of the antagonist was found useful in 

 the treatment of diphtheria carriers. 



Gramicidin S appears to be quite different from tyrothricin, since it 

 crystallizes readily when an alcoholic extract of the acid precipitate of 

 the bacterial culture is allowed to evaporate. It is four times more ef- 

 ficient in the killing of staphylococci than tyrothricin, although both 

 have similar toxicity. It is effective against various gram-negative bac- 

 teria, such as E. coli and P. vulgaris. Aqueous solutions (0.4 to 0.8 mg. 

 per ml.) were applied daily for 4 to 5 days to gunshot wounds of soft 

 tissues at the stage of necrosis, to severe burns, abscesses of the abdomi- 

 nal wall, and anaerobic infections j this was followed by gramicidin 

 ointments every 2 to 3 days, with highly favorable results. There was 

 no loss in potency in the presence of pus, no tissue irritation, with a 

 favorable effect on regeneration and epithelization (324, 589, 850). 

 The possible relation of the last phenomenon to cell malignancy has 

 been suggested (546). 



Subtilin and Bacitracin 



The toxicity index of subtilin has been defined (816) as the ratio of 

 the highest dilution of this antibiotic that kills embryonic chick heart 



