Use of Hela Cells Infected With Tubercle Bacilli for the Study of Anti-Tuberculous Drugs

It has been reported elsewhere that the growth of tubercle bacilli in HeLa cells in monolayer is rapid enough to be readily apparent in a few days (Shepard, 1955). T'he present paper describes a method for the employment of this convenient tissue culture system for the study of anti-tuber-culous drugs. Mackaness (1952), AMackaness and Smith (1952), and Suter (1952) have used rabbit and guinea pig macrophages in vitro to measure the activity of anti-tuberculous drugs and have pointed out that some of these drugs are not fully active against intracellular bacilli. Thus, the mini-mal inhibitory concentration of streptomycin in the macrophage system was 10 to 100 times more than it was in the usual test in bacteriological media, whereas the minimal inhibitory concentra-tion of isoniazid, isonicotinic acid hydrazide (INH) was the same in the macrophage system as in bac-teriological media. This difference between strep-tomycin and INH was thought to arise from a rela-tive impermeability of the cell membrane to streptomycin, so that the drug had to be present in excessive concentration in the extracellular fluid in order to achieve an adequate level within the cell. In contrast, the cell membrane was thought to be freely permeable to INH so that it was present in the same concentration within the cell as in the surrounding fluid. This conception took origin in the work of Magoffin and Spink (1951) who showed that brucella organisms were able to escape the action of streptomycin in bacteriological media if they were contained in human leucocytes. The factor of apparent permeability of the cell to the drug was taken into account in the experi-mental arrangement described below by the adop-tion of two alternative schedules for the adminis-tration of the drug. The two schedules were based on the observation that in this system the phago-I Presented in brief at the meeting of the Society of American Bacteriologists in Houston,