Detection of Acid-fast Bacillus in Healthy Mouse

Abstract

Nishimura and associates have reported that not only healthy mice but also non-leprous human skin are considerably contaminated with acid-fast bacillus, but as yet, there has been little information on such findings. Nishimura's observations have caused a non-neglectable problem in the conduction of experiments in which experimental animals are inoculated with leprosy or murine leprosy bacillus; and also in bacteriological examination of leprosy patients. Further investigations seemed justified and this study was undertaken to evaluate whether, and to what extent, healthy mouse could be infected with acid-fast bacillus.
Four groups of mice were used. Group A consisted of 21 CF#1 mice born and raised in an animal room used for mycobacterial-infected animals; Group B of 58 CF#1 mice born and allowed to remain, until the date of autopsy, with mice infected with murine leprosy; Group C of 25 dd-hybrid mice obtained from an unspecified source; and Group D of 46 CF#1 mice bred at random and raised under careful control in a room unrelated to mycobacterial-infected animals. For examination of acid-fast bacillus, foot-pad, dorsal skin, lung, liver, spleen and kidney were selected. These tissues were minced and ground with 2ml of a 1 per cent sodium hydroxide solution. The tissue suspension was transferred to a small test tube and left to stand for 30 minutes to allow settling of the heavy tissue elements. Oneml of the supernatant was decanted into a centrifuge tube, shaken with 0.1 ml of chloroform for 3 minutes, and centrifuged at 1, 000×g for 10 minutes. The chloroform button was placed on a spot-plate and stamped on a slide glass with a small glass rod. The slide was stained by carbol-fuchsin and Toda's solution. For each specimen, 200 oil-immersion fields were carefully examined for acid-fast bacillus.
As shown in the Table 1, acid-fast bacilli were detected in one of 21 mice in Group A, 9 of 58 in Group B, and none in Group C and D. Abundant bacilli were found in only one mouse in Group B. These results are not in agreement with Nishimura's reports. On the basis of our observation, it seems unlikely that acid-fast bacillus would be found so frequently in normal mice.