Multiple Mechanisms of^Drug ^Resistance 149 



An important conclusion is derived from a consideration of 

 the technique used for testing varying resistance during the 



lOO MO I20 



Time(mins) 



Fig. 5 a. Resistance to various concentrations of proflavine of cells 



in cultures of Esch. coli 36. Non-synchronized cultures. 

 A Tested from 80 min. after inoculation, on proflavine 4 (Jig./nil. 

 B Tested from 70 min. after inoculation, on proflavine O — 4-5 [xg./ml. 



#—5 {ig./ml. 



A— 5-7(^g./ml. 



X — 6-6 [JLg. I ml. 

 Time from inoculation. 



division cycles. We consider a cell to have a higher resistance 

 at one stage of the division cycle when it is able to produce 

 a colony on a plate with a higher concentration of proflavine. 



